n the sound of knocking (as on a door or in an engine or bearing)
v deliver a sharp blow or push :"He knocked the glass clear across the room"
v rap with the knuckles
v knock against with force or violence
v make light, repeated taps on a surface
v sound like a car engine that is firing too early
v find fault with; express criticism of; point out real or perceived flaws
[机] 爆震内燃机
1. I can hear someone knocking at the door.
我听到有人在敲门。
2. She was knocking on the window to get my attention.
她在窗户上敲打以引起我的注意。
3. He knocked loudly, hoping someone would answer.
他大声敲打，希望有人能回应。