Unforntunately, for any such definitions, it will depend on the individual situation in which the concept is being used. Typically physicists use Einstein's definition that "time is what is measured by a clock" but I think this is a bit too generic; after all, it is possible to use the physical dimensions of the clock to measure all sorts of things. Using this definition you have to then define what you mean by clock and it just gets more complicated from there.
My own personal definition of "time" would run something like:
Time is that property whereby one state of a well-defined system is transformed into another.
Again, the definitions of the words used becomes a complicating factor. I use "well-defined system" in a sense similar to how mathematicians use "well-behaved function." I mean a system that is logically coherent and consistent and follows the fundamental laws of nature.
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I should probably mention that the word "state" is also very misleading as the phrase "equation of state" for a system typically refers to a property that does not change with time. For example, the equation of state for an ideal gas is given by the ideal gas law $PV = nRT$. I would then say that time is the property of a system for which an equation of state can be written whereby the variables in that equation are transformed to different values.