Definition of tuck:
(v) :
to push in one material under another - as in "tuck in your shirt" or "I tucked in my shirt" etc; to eat food
"the diver tucked, flipped, and opened up at the last moment."
(n) :
snack food. Derived from the expression "to tuck in food" meaning "to eat up", "to guzzle"; a curled position