Entry 1 sense Webster, 1913 inst. · IPA 01 adj. in or of the present month; same as instant{3}, a. or instant{2}, n.; as, your letter of the 10th inst.. 1. in or of the present month; same as instant{3}, a. or instant{2}, n.; as, your letter of the 10th inst..[abbr.] See: instant, instant Syn. instant.