磕 (w)

(kē) to tap; knock

磕磕 (w)

(kēkē) knocking sound (onomatopoeia)

磕磕巴巴 (w)

(kēkēbābā) stammering; stuttering; not speaking fluently

磕磕绊绊 (w)

(kēkebànbàn) bumpy (of a road); limping (of a person)

磕头 (w)

(kētóu) to kowtow (traditional greeting, esp. to a superior, involving kneeling and pressing one's forehead to the ground)