Jack of all trades 似乎什么都懂的人
jolly dog（guy） 乐天派

jump on sb 向某人乱发脾气

jump the battery 充电

jumping the gun 迫不及待

just a minute 等一等；就来了；且慢

just as well 不如做某事也可

Just as you say. 好吧，随你的便

just follow suit 照办；跟进去

just for the fun of it 只不过好奇罢了

just the ticket， be 正是所需的

just too bad 太可惜；真糟糕

just what the doctor ordered 正合我的心意

keep a running account of 把教授在课堂讲的内容都记下来

keep a straight face 忍住不笑出来

keep an eye on 留意

keep an eye on sth 密切注意

keep body and soul together 继续活下去

keep company 陪伴

keep in touch with 联系

keep it to yourself 保密

keep it under your hat 保密

keep my fingers crossed 交叉手指，乞求某事成功

keep one's head 镇定

keep one's head above water 活下去

keep one's nose to the grand stone 孜孜工作

keep one's shirt on 不动手打架

keep pace with 保持同步

keep punching 继续努力