Source : Webster's Revised Unabridged Dictionary (1913)

Hibernal \Hi*ber"nal\, a. [L. hibernalis, from the root of hiems
   winter; akin to Gr. ? snow, Skr. hima cold, winter, snow: cf.
   F. hibernal.]
   Belonging or relating to winter; wintry; winterish. --Sir T.
   Browne.

Source : WordNet®

hibernal
     adj : characteristic of or relating to winter; "bears in brumal
           sleep" [syn: {brumal}, {hiemal}]