1. knock

英语释义：to repeatedly hit something, producing a noise

knock通常指用拳头或其他器械猛敲或猛打，也可指用手轻敲某物。

She knocked on the window to attract his attention.

她敲敲窗想引起他的注意。

There's someone knocking on/at the door.

有人在敲门。

2. tap

英语释义：to hit something gently, and often repeatedly, especially making short, sharp noises

tap多指慢慢地、连续地轻击或轻拍。

She tapped her girl to let her sleep.

她轻轻拍着女儿让她睡觉。

He tapped his forehead knowingly.

他会心地拍拍前额。

3. rap

英语释义：to hit or say something suddenly and forcefully

rap的本意是“敲击，急拍”，指用手指或木棒等快速地轻敲或急拍，发出刺耳的声音使人们静下来。

She rapped (on) the table to get everyone's attention.

她敲了敲桌子，让大家注意。

The colonel rapped (out) an order to his men.

上校厉声对他的士兵下命令。

4. pet

英语释义：If you pet an animal, child, etc., you touch it, him, or her gently and kindly with your hands.

pet的意思是“宠爱，抚摸”，多指宠爱或抚摸动物。

Our dog loves to be petted and tickled behind the ears.

我们的狗喜欢人在它耳后抚摸、挠痒。

5. pat

英语释义：to touch someone or something gently and usually repeatedly with the handflat

pat的意思是“轻拍，轻打”，指用手轻拍以示同情、赞同或爱抚。所以说，我觉得这个词最适合描述“摸头杀”啦。

He patted my head/patted me on the head tenderly.

他温柔地拍了拍我的头。