Merriam-Webster's Collegiate® Dictionary, 11th Edition
INSTANT
I. noun
Etymology: Middle English, from Anglo-French, from Medieval Latin instant-, instans, from instant-, instans, adjective , instant, from Latin
Date: 14th century
an infinitesimal space of time, the present or current month,
II. adjective see: stand
Date: 15th century
importunate , urgent ,
2. present , current , of or occurring in the present month, immediate , direct ,
4. a. premixed or precooked for easy final preparation , appearing in or as if in ready-to-use form , immediately soluble in water , produced or occurring with or as if with extreme rapidity and ease, instantness noun