Given to unplanned and silly ideas or actions.
That flies easily or often.
nonstandard; not conforming to rules or expectations
without symmetry, regularity, or uniformity
rough
not regular; having sides that are not equal or angles that are not equal
whose faces are not all regular polygons (or are not equally inclined to each other)
not following the regular or expected patterns of inflection in a given language
A soldier who is not a member of an official military force and who may not use regular army tactics.
One who does not regularly attend a venue.