short for substitute: a sports player who is used for part of a game instead of another player

One of the players was injured during the match, so a sub was brought on. 比赛中一个队员受了伤，于是一个替补队员顶上了。

See also: substitute noun

short for substitute teacher: a teacher who replaces teachers who are absent from work

A trained teacher, he found work as a sub, which fitted around his other commitments. 他是一名受过培训的教师，他觉得做代课老师这样的工作便于他做其他事情。

short for submarine: a ship that can travel underwater

a nuclear sub 核潜艇

short for subscription: an amount of money that you pay regularly to be a member of an organization or club

Have you paid your tennis club sub yet? 你付过网球俱乐部的会费了吗？

short for submarine sandwich: a long, thin loaf of bread filled with meat or cheese, and often lettuce, tomatoes, etc.

a meatball sub 肉丸潜艇三明治

short for substitute: to play in a sports match in someone's place

Travis subbed for the injured defender. 特拉维斯替换受伤的后卫上场。

short for substitute: to do a job temporarily when someone else cannot do it

As a young player, he subbed for Duke Ellington's drummer. 年轻时，他曾做过艾灵顿公爵的替补鼓手。

I subbed as a teacher for a semester. 我当过一个学期的代课老师。

short for substitute: to replace one player with another during a game

He was subbed in the match against Newcastle. 他在对纽卡斯联队的比赛中被替换下场了。

less than a number or level

Winter weather brought sub-zero (= less than 0 degrees) temperatures to much of the country. 冬天国内许多地方的气温降到了零度以下。

smart TVs in the sub-$1000 price range 价位在1000美元以下的智能电视

the first man to run a sub-4 minute mile 第一个花了不到4分钟时间跑完1英里的人

below or in a lower position

the subarctic 亚北极的

a sub-layer 亚层

almost or nearly

subtropical 亚热带的

being a smaller part of a larger whole

a subcontinent 次大陆

a subcommittee meeting 小组委员会会议

to subdivide 再分

not as good as

subhuman 低于人类的

a sub-standard effort 不及格的努力

The film is a sort of sub-Godfather mafia family tale. 这部电影算是一部不够《教父》水平的黑帮家族故事影片。

less important or lower in rank

a sub-deacon 副主祭

a subordinate 部属