latch

Concise Oxford English Dictionary © 2008 Oxford University Press:
latch/latʃ/

▶noun

• 1 a bar with a catch and lever used for fastening a door or gate.

• 2 a spring lock for an outer door, which catches when the door is closed and can only be opened from the outside with a key.

• 3 Electronics a circuit which retains whatever output state results from a momentary input signal until reset by another signal.

▶verb

• 1 fasten with a latch.

• 2 Electronics (of a device) become fixed in a particular state.

• 3 (latch on) informal understand the meaning of something.

• 4 (latch on to) informal attach oneself to (someone) as a constant companion.

  ■ take up (an idea or trend) enthusiastically.

• 5 (latch on) (of a breastfeeding baby) manage to get its mouth into the correct position around the nipple.

– phrases
on the latch chiefly Brit. (of a door or gate) closed but not locked.

– origin OE læccan ‘take hold of, grasp’, of Gmc origin.