Meaning of LATCH in English

I. latch 1 /lætʃ/ BrE AmE noun [countable]

1 . a small metal or plastic object used to keep a door, gate, or window closed:

Gwen lifted the latch and opened the gate.

2 . especially British English a type of lock for a door that you can open from the inside by turning a handle, but that you need a key to open from the outside

on the latch (=shut but not locked)

Ray went out, leaving the door on the latch.

II. latch 2 BrE AmE verb [transitive]

[ Language: Old English ; Origin: læccan ]

to fasten a door, gate, or window with a latch

latch on phrasal verb

British English informal to understand:

He’s so thick it took him ages to latch on.

latch onto somebody/something ( also latch on to somebody/something ) phrasal verb informal

1 . to become very interested in something:

Don’t just latch on to the latest management fads.

2 . to follow someone and keep trying to talk to them, get their attention etc, especially when they would prefer to be left alone:

He latched onto Sandy at the party and wouldn’t go away.

3 . to hold tightly to something with your hand, mouth etc:

a baby latching on to its mother’s breast

Longman Dictionary of Contemporary English.      Longman - Словарь современного английского языка.