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 from outside
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 again
4. to fasten, fit, or be fitted with or as if with a latch