Exact historical dictionary sense
Better in Webster's 1913 dictionary
The 1913 record labels better as adjective. Its source-bounded etymology and selected historical definition appear below.
[OE. betere, bettre, and as adv. bet, AS. betera, adj., and bet, adv.; akin to Icel. betri, adj., betr, adv., Goth. batiza, adj., OHG. bezziro, adj., baz, adv., G. besser, adj. and adv., bass, adv., E. boot, and prob. to Skr. bhadra excellent. See Boot advantage, and cf. Best, Batful.]
Cross-verified historical senseIn Webster's Revised Unabridged Dictionary (1913), "better" is labeled adjective. Its etymology is recorded as: "[OE. betere, bettre, and as adv. bet, AS. betera, adj., and bet, adv.; akin to Icel. betri, adj., betr, adv., Goth. batiza, adj., OHG. bezziro, adj., baz, adv., G. besser, adj. and adv., bass, adv., E. boot, and prob. to Skr. bhadra excellent. See Boot advantage, and cf. Best, Batful.]" The selected historical definition says: "Having good qualities in a greater degree than another; as, a better man; a better physician; a better house; a better air."