nod

Concise Oxford English Dictionary © 2008 Oxford University Press:
nod/nɒd/

▶verb (nods, nodding, nodded)

• 1 lower and raise one's head slightly and briefly, especially in greeting, assent, or understanding, or as a signal.

  ■ signify or express in this way: he nodded his consent.

  ■ (nod something through) informal approve something by general agreement and without discussion.

  ■ move one's head up and down repeatedly.

• 2 let one's head fall forward when drowsy or asleep.

  ■ (nod off) informal fall asleep.

  ■ make a mistake due to a momentary lack of attention.

  [with allusion to L. dormitat Homerus ‘even Homer nods’ (Horace Ars Poet. 359).]

• 3 Soccer head (the ball) in a specified direction without great force.

▶noun an act of nodding.

■ a gesture of acknowledgement or concession.

– phrases
a nodding acquaintance a slight acquaintance.
be on nodding terms know someone slightly.
give someone/thing the nod

• 1 select or approve someone or something.

• 2 give someone a signal.

on the nod Brit. informal

• 1 by general agreement and without discussion.

• 2 dated on credit.

– origin ME: perh. of Low Ger. origin.