verb

make a quick, short movement up and down.

I could see his head bobbing about

bounce,move up and down,float,spring,toss,skip,hop,dance,jump,jounce,quiver,wobble,jiggle,joggle,jolt,jerk,shake,oscillate,nod,incline,bow,dip,duck,wag,waggle

noun

a quick, short movement up and down.

she could only manage a slight bob of her head

nod,inclination,bow,dip,duck,wag,waggle