When you nod, you shake your head up and down, as if you're indicating agreement. If you want to say "Yes" without uttering a single word, all you have to do is nod.

There's the deliberate nod, when you agree with someone by raising and lowering your chin, and then there's the accidental nod — when you're so sleepy that your eyes close and your head dips down. You can even say you "nod off to sleep" in this case. If you know someone well enough to nod at them when you pass, but not well enough to stop and chat, you can call that person "a nodding acquaintance."

Definitions of nod

v lower and raise the head, as to indicate assent or agreement or confirmation

“The teacher nodded when the student gave the right answer”
Type of:
communicate, intercommunicate
transmit thoughts or feelings

v express or signify by nodding

“He nodded his approval”
Type of:
gesticulate, gesture, motion
show, express or direct through movement

v let the head fall forward through drowsiness

“The old man was nodding in his chair”

v be almost asleep

“The old man sat nodding by the fireplace”
Type of:
be on the verge of sleeping

v sway gently back and forth, as in a nodding motion

“the flowers were nodding in the breeze”
Type of:
move so as to change position, perform a nontranslational motion

n the act of nodding the head

uncontrolled nodding
Type of:
inclination, inclining
the act of inclining; bending forward

n a sign of assent or salutation or command

Type of:
gesture, motion
the use of movements (especially of the hands) to communicate familiar or prearranged signals

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