rat-tat

(also rat-a-tat / 9rt E 5tt;9rAtE`tAt/, rat-a-tat-tat / 9rt E tt 5tt; 9rAtE9tAt`tAt/) n [sing] sound of rapping or knocking, esp on a door 砰砰的敲击声; （尤指）敲门声: a sharp rat-tat at/on the front door 敲击正门的响亮声音.

rarefaction, rarefied, rarefy, rarely, rareness, raring, rarity, rascal, rascally, rase, rash, rasher, rashly, rashness, rasp, raspberry, raspy, Rastafarian, rat, rat-a-tat-tat, ratatat, ratbag, ratchet, rate, rate-capping, rateable, ratepayer, ratfink, rather, rather than, rather too, ratification, ratify, rating, ratio, ratiocination, ration, rational, rationale, rationalism,