(1):

(v. t.) To fix the bounds of; to bring to a termination; to end.

(2):

(v. i.) To determine; to decide.

(3):

(v. t.) To determine the precise signification of; to fix the meaning of; to describe accurately; to explain; to expound or interpret; as, to define a word, a phrase, or a scientific term.

(4):

(v. t.) To determine with precision; to mark out with distinctness; to ascertain or exhibit clearly; as, the defining power of an optical instrument.

(5):

(v. t.) To determine or clearly exhibit the boundaries of; to mark the limits of; as, to define the extent of a kingdom or country.