Latch  —n. 1 bar with a catch and lever as a fastening for a gate etc. 2 spring-lock preventing a door from being opened from the outside without a key. —v. Fasten with a latch.  latch on (often foll. By to) colloq. 1 attach oneself (to). 2 understand. On the latch fastened by the latch (sense 1) only. [old english]