The Collaborative International Dictionary
Trifallow
Trifallow \Tri"fal`low\, v. t. [imp. & p. p. Trifallowed; p.
pr. & vb. n. Trifallowing.] [Pref. tri- + fallow. Cf.
Thryfallow.]
To plow the third time before sowing, as land.
--Mortimer.
Wiktionary
trifallow
vb. (context obsolete rare English) To plough (land) the third time before sowing.