(of a door or gate) closed but not locked（门）关着但没锁上
latch on
(of a breastfeeding baby) manage to get its mouth into the correct position around the nipple（哺乳婴儿）用嘴叼到乳头
latch on to informal 非正式
attach oneself to (someone) as a constant and usually unwelcome companion纠缠understand the meaning of (something)理解，明白
latch on to 或 latch onto
To get hold of; obtain取得；得到
柯林斯高阶英汉双解学习词典释义
N-COUNT
门闩；插销
A latch is a fastening on a door or gate. It consists of a metal bar which you lift in order to open the door.
例句
You left the latch off the gate and the dog escaped.你没把门闩插上，所以狗跑了。
N-COUNT
碰锁；弹簧锁
A latch is a lock on a door which locks automatically when you shut the door, so that you need a key in order to open it from the outside.
例句
...a key clicked in the latch of the front door.钥匙插进前门弹簧锁里发出咔嗒一声
VERB
用闩闩上；用碰锁锁上
If you latch a door or gate, you fasten it by means of a latch.
例句
He latched the door, tested it, and turned around to speak to Frank.他把门锁上，又试了试，然后转身和弗兰克说话。
英汉词典释义
n.
(门窗的)门闩
To open the gate, lift up the latch.要打开大门, 先把门闩提起来。
vt. & vi.
用碰锁锁上(门等);闩上(门等)
Remember to latch the gate behind you.记住出门时把大门闩上。
纠缠，缠住(某人)
He latched onto us and we couldn’t get rid of him.他缠着我们，甩也甩不掉。
附着(在某物上)
The virus latches onto the red blood cells.这种病毒附着在红细胞上。
对…产生兴趣(并加以利用)
The government have latched onto environmental issues to win votes.政府已开始大谈环境问题以争取选票。They have a reputation for latching onto all the latest crazes.大家都知道他们对所有的最新时尚都有兴趣。Young children latch onto phrases and repeat them over and over.小孩子喜欢成语，一遍遍地重复。
理解，懂得，领会(想法或某人的话等)
It took him a while to latch onto their style of humour.他过了一会儿才明白他们的幽默方式。She soon latched onto the idea.她很快就理解了这个想法。It was a difficult concept to grasp, but Sam latched on very quickly.那是个难掌握的概念，但萨姆很快就理解了。
英英词典释义
Noun
1. spring-loaded doorlock that can only be opened from the outside with a key
2. catch for fastening a door or gate; a bar that can be lowered or slid into a groove