Entry 3 senses · 3 variants Webster, 1913 Milt /mĭlt/ · IPA /mɪlt/ n. n. v. t. 01 n. The spleen. 1. The spleen.(Anat.) 02 n. The spermatic fluid of fishes. 1. The spermatic fluid of fishes.(Zool.) 03 v. t. To impregnate (the roe of a fish) with milt. 1. To impregnate (the roe of a fish) with milt.