the short, thick finger at the side of the hand, slightly apart from the other four 拇指 
Extra ExamplesTopics Bodyb2He smiled and raised a thumb in greeting. 他微微一笑，竖起拇指表示问候。 I picked up the beetle carefully between finger and thumb. 我用食指和拇指小心地捏起甲虫。 I stuck out a thumb and a car stopped immediately. 我伸出大拇指，马上有一辆车停了下来。
Oxford Collocations Dictionaryverb + thumb- suck
- flick
- jab
- …
- nail
- between finger and thumb
- between thumb and forefinger
- thumbs up
- …
the part of a glove that covers the thumb （手套的）拇指部分
Word OriginOld English thūma, of West Germanic origin; related to Dutch duim and German Daumen, from an Indo-European root shared by Latin tumere ‘to swell’. The verb dates from the late 16th cent., first in the sense ‘play (a musical instrument) with the thumbs’.
Idioms
be all (fingers and) thumbs
to be awkward with your hands so that you drop things or are unable to do something 笨手笨脚；笨拙；手指不灵活
hold thumbs
- (South African English)
to hope that your plans will be successful or that something will take place in the way that you want it to 希望（计划）成功；期望如愿以偿
a rule of thumb
a practical method of doing or measuring something, usually based on past experience rather than on exact measurement 实用的估算方法，经验工作法（常依据经验而非准确测量） As a rule of thumb, you should cook a chicken for 20 minutes for each pound of weight. 根据经验，每磅重量你应该煮一只鸡20分钟。
stand/stick out like a sore thumb
to be very easy to notice in an unpleasant way 招眼；扎眼 The blue building stood out like a sore thumb among the whitewashed villas. 这座蓝色建筑在粉刷过的别墅中显得格外显眼。 If you wear a suit to the party, you’ll stand out like a sore thumb. 如果你穿西装去参加聚会，你会非常显眼。
thumbs up/down
- (informal)
used to show that something has been accepted/rejected or that it is/is not a success 跷拇指（表示接受或成功）；拇指向下（表示拒绝或不成功） Their proposals were given the thumbs down. 他们的建议遭到拒绝。 It looks like it's thumbs up for their latest album. 看样子他们的最新歌曲专辑成功了。 He made a thumbs-up sign through the window to tell us everything was fine. 他隔着窗子竖起大拇指，告诉我们一切顺利。
twiddle your thumbs
to move your thumbs around each other with your fingers joined together 抱手旋弄大拇指 to do nothing while you are waiting for something to happen （等待之际）无所事事 We can't just sit here twiddling our thumbs and hoping everything will be all right. 我们不能坐在这里无所事事，希望一切都会好起来。
under somebody’s thumb
- (informal)
(of a person 人 completely controlled by somebody 完全受人支配；受制于人 She’s got him under her thumb. 她把他管住了。