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

(literary) to inquire

to express one's sincere gratitude by kowtow

to knock on a door

to kowtow in salute

call-in (loanword)

to kowtow

to visit (esp. one's superiors)

to knock at the gate (old)

spike (volleyball)

to kowtow

to bow in salute; to kowtow

to kneel three times and kowtow nine times (formal etiquette on meeting the emperor)