knock 指用拳头或其它器械猛敲或猛打；也指用手轻敲某物。
tap 多指慢慢地连续地轻击或轻拍。
rap 指用手指或木棒等快速地轻敲或急拍。
pat 指用手轻拍以示同情、赞同或爱抚。
参考例句
1. The medicine is effective for knocking colds. 这种药祛除感冒很有效。
2. Yet people still knock him. 人们还是想击溃他。
3. Does the bad man knock over the trees with the black car? 这个坏人用这辆黑色汽车把这些树撞倒了吗?
英英解释
n.
1. the sound of knocking (as on a door or in an engine or bearing)
2. negative criticism
3. a vigorous blow
4. a bad experience
5. the act of hitting vigorously v.
1. deliver a sharp blow or push :
2. rap with the knuckles
3. knock against with force or violence
4. make light, repeated taps on a surface
5. sound like a car engine that is firing too early
6. find fault with; express criticism of; point out real or perceived flaws
网络释义
knock 敲，敲打;
敲门;
敲缸;
敲击;
Knock back 反座;
（摇把）反击，（活塞）逆行，（曲轴）反转;
回击;
使...大吃一惊;
knock up 码纸;
筋疲力尽;
匆匆安排 使精疲力尽 [英](板球赛中)很快得分 [美俚](指男人)与...通奸;
叫醒;
