Lewis & Short

fustis, is (abl. fusti, Plaut. As. 2, 4, 21; id. Capt. 4, 2, 116; Val. Max. 6, 3, 9; Tac. A. 14, 8 al., or fuste, Hor. S. 1, 3, 134; 1, 5, 23; 2, 3, 112; Juv. 9, 98; Val. Max. 8, 1, 1; Dig. 9, 2, 7, § 1 al.), m. [through the forms fonstis, fond-tis, from root of -fendo, found in offendo, defendo, etc.; cf.: mani-festus, in-festus, con-festim, festino; Gr. θείνειν, to strike, Curt. Gr. Etym. p. 255; Corss. Ausspr. 2, 190], a knobbed stick, a cudgel, staff, club (syn.: sceptrum, scipio, ferula, baculum): tamquam si claudus sim, cum fusti est ambulandum, Plaut. As. 2, 4, 21; Varr. L. L. 5, § 137 Müll.: severae Matris ad arbitrium recisos Portare fustes, Hor. C. 3, 6, 41; for threshing out grain: ipsae spicae melius fustibus cuduntur, Col. 2, 20, 4.
Esp. for cudgelling: auferere, non abibis, si ego fustem sumpsero, Plaut. Am. 1, 1, 202: male mulctati clavis ac fustibus, Cic. Verr. 2, 4, 43, § 94: non opus est verbis, sed fustibus, id. Pis. 30, 73: si filius meus fustem mihi impingere volet? Cael. ap. Cic. Fam. 8, 8, 9: quos tu nisi fuste coërces, Hor. S. 1, 3, 134: mulae caput fuste dolare, id. ib. 1, 5, 22: fuste aperire caput, Juv. 9, 98: injuria committitur cum quis fuste percussus erit, Gai Inst. 3, 220: fustium admonitio, Dig. 48, 19, 7.
And for beating to death, as a milit. punishment (v. fustuarium): sorte ductos fusti necat, Sall. H. Fragm. 4, 5 Dietsch: primipili centurionem ob turpem ex acie fugam fusti percussit, Vell. 2, 78 fin.; Tac. A. 3, 21; Front. S. 4, 1, 34 Oud.; Auct. B. Hisp. 27 fin.; Paul. Sent. 5, 18, 1; 5, 21, 1.
Hence: formidine fustis (i. e. to be beaten to death) ad bene dicendum redacti, Hor. Ep. 2, 1, 154.