(1):

(n.) A small shoot or branch of a tree or other plant, of no definite length or size.

(2):

(v. t.) To beat with twigs.

(3):

(v. t.) To twitch; to pull; to tweak.

(4):

(v. t.) To understand the meaning of; to comprehend; as, do you twig me?

(5):

(v. t.) To observe slyly; also, to perceive; to discover.