The Collaborative International Dictionary
Loppering
Lopper \Lop"per\, v. i. [imp. & p. p. Loppered; p. pr. & vb. n. Loppering.] [Cf. Prov. G. l["u]bbern, levern, OHG. giliber[=o]n, G. luppe, lab, rennet.] To turn sour and coagulate from too long standing, as milk.
Wiktionary
loppering
vb. (present participle of lopper English)