chi�me�ra or chi�mae�ra \ki-'mir-a, ka-\ n [L chimaera, fr. Gk chimaira she-goat, chimera; akin to Gk cheimon winter - more at HIBERNATE] 1 a cap : a fire-breating she-monster in Greek mythology having a lion's head, a goat's body, and a serpent's tail b : an imaginary monster compounded of incongruous parts 2 : an illusion or fabrication of the mind; esp : an unrealizable dream <a fancy, a ~ in my brain, troubles me in my prayer -John Donne> 3 : an individual, organ, or part consisting of tissues of diverse genetic constitution and occurring esp. in plants and most fequently as a graft union