1. a fastening for a gate or door that consists of a bar
that may be slid or lowered into a groove, hole, etc.
2. a spring-loaded door lock that can be opened by a key
3. Also called: latch circuit (electronics) a logic circuit
that transfers the input states to the output states when signalled, the output
thereafter remaining insensitive to changes in input status until signalled
4. to fasten, fit, or be fitted with or as if with a latch