Liquid column "recoils" in a sealed cylinder when hit by a piston -- is it possible? Consider a cylinder filled partially with a liquid (e.g. water). The cylinder is sealed, and is at held at room temperature (e.g 298K). At equilibrium (or when no external disturbance is imparted to the system), the liquid in the cylinder exists in equilibrium with its vapor at the vapor pressure of the liquid, applicable at room temperature.
Suppose that the bottom of the cylinder is fitted with a piston. Note that the system is still sealed. Now imagine that the piston moves upwards. The liquid column moves upwards, the volume the vapor occupies decreases, but the vapor still exists at the vapor pressure of the liquid (assuming that thermodynamic equilibrium can be achieved fast enough).
What's interesting is when the piston move downwards. If the piston moves at a slow speed, the liquid column should stay "on top of" the piston (without any "gap" between the column and the piston). Now, if the piston moves downwards fast enough (or when the downward acceleration is high enough), the liquid column shall "leave" the piston, and a "packet" of vapor shall be formed between the piston and the liquid column. (Please refute the former claim if you think it's wrong.) Why? if the "friction" between the cylinder walls and the liquid column is negligible, and the liquid column is already in a state of free-falling, there is no mechanism to "pull" it downwards further anymore.
Now, imagine that the piston moves upwards again. Then the liquid column shall "collide" with the piston. Will it "stick" to the piston, as in an inelastic collision, or recoil, as in an elastic collision? 
P.S. After thinking for a while, I think it is not at all an easy question to answer. Now whether the liquid will "recoil" (not "slosh", which implies that the liquid changes shape) depends on how momentum is transferred from the piston to the liquid column. Please refer to the youtube video for the "beer bottle trick". If the cavity formed at the bottom is a "vacuum", which is probably the case, then when the liquid "smash back", the atmospheric pressure shall press on the liquid column, and most probably it will not "recoil". On the other hand, if the cavity formed is gas-filled, then the kinetic energy from the liquid (which is trying to "smash back" on the glass bottle) may be dissipated to the gas (in the original gas-filled cavity), through the formation of many tiny cavitations (claim: the latter claim is not sound; I am just guessing). For as long as the impact is "dampened", a recoil will not happen.
Indeed there are many ways in which a liquid may dissipate energy, because it's formless/shapeless, and there's viscosity in the picture. The more "flexible" it is to energy dissipation, the less likely it is to recoil. 
 A: Your question is somewhat more "general" than what is implied.  You are essentially talking about cavitation (or getting very close to talking about it).  Cavitation does not require slugs of liquid traveling downward.  In fact, there are internet pictures showing ship propeller designs where the engineers didn't account for the pressure drop on the downstream side of the propeller.  If the pressure gets below the vapor pressure of the liquid, the liquid "boils" over a very short time interval, and when the pressure rises substantially, the associated small vapor bubbles instantly collapse.  When the collapse happens, the vapor bubble temperature rises dramatically and a very small shock wave is formed.  If this collapse happens to occur on the metal surface, the shock wave WILL remove small bits of metal.  If this condition persists, the propeller will be worn away.
If you are wondering how high the bubble temperature can get, there are experiments whereby ultrasound is used to deliberately create cavitation in bulk liquids.  When the bubbles collapse, the temperature gets high enough to emit a very small flash of light, and the process is called sonoluminescence.  Measurements indicate that the temperatures that produce this small flash of light are higher than the temperature at the surface of the sun, so while the process within one of these bubbles is extremely small, it is also extremely violent.
A: Because of gravitational forces you liquid is at the bottom of both phases.
A pressure gradient, due to those forces exist in both phases; the pressure increases linearly through bot fluid, with a discontinuous ramp at the interface liquid/gaz.
So if you push down the piston, by increasing the volume you will modify the equilibrium point and so decrease the equilibrium pressure. The only way you can create an extra gaz volume is by cavitation of the fluid, which can only occur at the minimal pressure point of the liquid i.e the fluid/gaz interface. So I think you can't actually create some kind of "gap" between the piston and the liquid, as far as your piston speed is lower than the sound speed (the pressure information will be faster than the piston and so create evaporation at the interface to balance the volume modification). 
If you piston is faster than sound velocity over liquid water (really?) I think you can actually create a local dilatation and so bubbles at the bottom of the fluid. This non stationary evolution is certainly really hard to model. 
