Entry 2 senses · 2 variants Webster, 1913 Hypo /hīp'-ō/ · Hy·po · IPA /ˈhaɪ.poʊ/ n. n. 01 n. Hypochondria. 1. Hypochondria.[Colloq.] 02 n. Sodium hyposulphite, or thiosulphate, a solution of which is used as a bath to wash out the unchanged silver salts in a picture. 1. Sodium hyposulphite, or thiosulphate, a solution of which is used as a bath to wash out the unchanged silver salts in a picture.(Photog.) [Colloq.]