What does "regular" mean?

Regular: Governed by rule or rules; steady or uniform in course, practice, or occurence; not subject to unexplained or irrational variation; returning at stated intervals; steadily pursued; orderlly; methodical; as, the regular succession of day and night; regular habits.

Additional senses

  1. 2.Constituted, selected, or conducted in conformity with established usages, rules, or discipline; duly authorized; permanently organized; as, a regular meeting; a regular physican; a regular nomination; regular troops.
  2. 3.Belonging to a monastic order or community; as, regular clergy, in distinction dfrom the secular clergy.
  3. 4.Thorough; complete; unmitigated; as, a regular humbug. [Colloq.]
  4. 5.(Bot. & Zoöl.) Having all the parts of the same kind alike in size and shape; as, a regular flower; a regular sea urchin.
  5. 6.(Crystallog.) Same as Isometric. Regular polygon (Geom.), a plane polygon which is both equilateral and equiangular. -- Regular polyhedron (Geom.), a polyhedron whose faces are equal regular polygons. There are five regular polyhedrons, -- the tetrahedron, the hexahedron, or cube, the octahedron, the dodecahedron, and the icosahedron. -- Regular sales (Stock Exchange), sales of stock deliverable on the day after the transaction. -- Regular troops, troops of a standing or permanent army; -- opposed to militia. See Normal.
  6. 7.(R. C. Ch.) A member of any religious order or community who has taken the vows of poverty, chastity, and obedience, and who has been solemnly recognized by the church. Bp. Fitzpatrick.
  7. 8.(Mil.) A soldier belonging to a permanent or standing army; -- chiefly used in the plural.

Sources