breathing in breat·hin·gin uncommon noun 1. the act of inhaling; the drawing in of air (or other gases) as in breathing Synonymsinhalationinspirationaspirationbreathing in Related words Word family aspirateinspireinhale Broader terms breath Narrower terms gasppuff Parts breathing WordNet 2.1 (Princeton University). WordNet 2.1 Copyright Princeton University. All rights reserved.