Lewis & Short

Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.

lētālis (lēthāl-), e, adj. [letum], deadly, fatal, mortal (mostly poet. and late Lat.): vulnus, Verg. A. 9, 580; Suet. Caes. 82: harundo, Verg. A. 4, 73; ensis, Ov. M. 13, 392: serpens, Stat. Th. 6, 40: dapes, Val. Fl. 2, 155: hiems, Ov. M. 2, 827: venenum, Plin. 11. 35, 41, § 118: lac gustasse letale est, id. 11, 41, 96, § 236; Aug. Serm. 351, 5: ferrum, Juv. 15, 165.
In neutr., adverbially, in a deadly manner: letale minari, Stat. S. 4, 4, 84: letale furens, id. Th. 12, 760.
Plur. subst.: lētālĭa, ium, means of death, Liv. 8, 18, 7.
Hence, adv.: lētālĭter, in a deadly manner, mortally, Plin. 11, 37, 81, § 206: vulneratus, Mos. et Rom. Leg. Coll. 2, 7 prooem.