Projectile motion with or without air resistance It is unclear to me if we can call a motion a projectile motion or an object a projectile if there is involved air resistance. Some sources say that a projectile is only affected by the acceleration due to gravity, and other sources say that a projectile is an object subjected only to the acceleration due to gravity and air resistance. So, what should be the clearer explanation for this ambiguity [in my perspective]?
 A: Yes I think we can.

Source: University Physics - Sears & Zemansky
For a clearer explanation we can also go for the origin of the word 'projectile'.
"body projected or impelled forward by force," 1660s, from Modern Latin projectilis. Usually used for a missile fired from a gun.
Hope this Helps.
A: Yes, we can.  Projectile motion can be understood, as the name suggests, the motion experienced by a body projected into air, whose path is usually curved. When we talk about kinematics, we do not consider the nature of object, so whenever a statement reads, "a body is projected" we assume it to be a point mass, which is theoretically dimensionless. Now, The projectile motion is largely related to kinematics rather than dynamics, in which we discuss about the cause of this motion i.e. forces in general. These forces depend on various other parameters (such as mass , surface area, cross-sectional area, friction coefficient, drag coefficient, nature of medium, etc). Bodies which appear in projectile motion do feel air resistance but we don't consider it because during discussions regarding kinematics, we only see the acceleration produced by this force, which is very weak in comparison to acceleration due to gravity.  So, practically, projectile motion has noting to do with air resistance. Hence it is correct to use the term projectile motion to describe a motion under acceleration due to gravity and air resistance since its effect is however nullified by the comparatively huge magnitude of gravitational force.
You can visit the below link to know about the actual magnitude of this force and its practical effects. When Does the Air Resistance Force Make a Difference? 
-Rhett Allian
Thank you.
