Acircumscribed elevation of the skin containing a non-purulent fluid is known as a(n)

The answer to this question would be : vesicle or bullae.

If the size of the elevation is <0.5cm it is called vesicle but if it's larger it called bullae. The fluid inside vesicle and bullae is clear. Vesicle and bullae that caused by infection can become purulent after a period of time, thus called pustule.