/bʌk ||; bʌk/verb [I] (used about a horse) to jump into the air or to kick the back legs in the air （指马）四蹄离地跃起 buck (sb/sth) up(informal 非正式) to feel or to make sb feel better or happier （使）振奋: Drink this -- it'll buck you up. 喝了这一杯，你会振作起来的。Unless you buck your ideas up (= become more sensible and serious), you'll never pass the exam. 要是你不振作精神，考试永不会及格。