movement, motility, motion, move - a change of position that does not entail a change of location; "the reflex motion of his eyebrows revealed his surprise"; "movement is a sign of life"; "an impatient move of his hand"; "gastrointestinal motility"

bob - a short abrupt inclination (as of the head); "he gave me a short bob of acknowledgement"

nod - the act of nodding the head

stoop - an inclination of the top half of the body forward and downward