Running or performing extremely smoothly, especially (music, slang) playing perfectly, perfectly in sync with others, or with perfect focus.
Used other than figuratively or idiomatically: see in, groove.
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)
nonstandard; not conforming to rules or expectations
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.