A soldier who is not a member of an official military force and, often, does not follow regular army tactics
One who does not regularly attend a venue
Nonstandard; not conforming to rules or expectations
(of a surface) rough
Without symmetry, regularity, or uniformity
(of a polygon) not regular; having sides that are not equal or angles that are not equal
(of a polyhedron) whose faces are not all regular polygons (or are not equally inclined to each other)
(grammar, of a word) not following the regular or expected patterns of inflection in a given language