The Collaborative International Dictionary of English v.0.48:

Tigress \Ti"gress\, n. [From Tiger: cf. F. tigresse.] (Zool.)
   The female of the tiger. --Holland.
   [1913 Webster]

WordNet (r) 3.0 (2006):

tigress
    n 1: a female tiger

Moby Thesaurus II by Grady Ward, 1.0:

93 Moby Thesaurus words for "tigress":
   Jezebel, Mafioso, Partlet, Young Turk, battle-ax, beast, beldam,
   berserk, berserker, biddy, bitch, bitch-kitty, bomber, bossy,
   brood mare, brute, cat, common scold, cow, demon, devil, doe,
   dragon, ewe, ewe lamb, fiend, filly, fire-eater, firebrand,
   fishwife, fury, goon, gorilla, grimalkin, guinea hen, gunsel, gyp,
   hag, hardnose, heifer, hell-raiser, hellcat, hellhag, hellhound,
   hellion, hen, hind, holy terror, hood, hoodlum, hothead, hotspur,
   incendiary, jenny, killer, lioness, mad dog, madcap, mare, monster,
   mugger, nanny, nanny goat, peahen, rapist, revolutionary, roe,
   savage, scold, she-bear, she-devil, she-goat, she-lion, she-wolf,
   shrew, siren, slut, sow, spitfire, termagant, terror, terrorist,
   tiger, tough, tough guy, ugly customer, violent, virago, vixen,
   wild beast, wildcat, witch, wolf