rapid

Từ điển American Heritage Dictionary 4th

rap·id (răpʹĭd)adj. rap·id·er, rap·id·est
Moving, acting, or occurring with great speed. See Synonyms at fast¹.n.
An extremely fast-moving part of a river, caused by a steep descent in the riverbed. Often used in the plural. [Latin rapidus, from rapere, to seize. See rep- in Indo-European Roots.] ra·pidʹi·ty (rə-pĭdʹĭ-tē) or rapʹid·ness (răpʹĭd-nĕs) n.rapʹid·ly adv.