Entry 2 senses · 2 variants Webster, 1913 Lopper · Lop·per · IPA n. v. i. 01 n. One who lops or cuts off. 1. One who lops or cuts off. 02 v. i. To turn sour and coagulate from too long standing, as milk. imp. & p. p. Loppered; p. pr. & vb. n. Loppering 1. To turn sour and coagulate from too long standing, as milk.