The Collaborative International Dictionary of English v.0.48:

Tiglic \Tig"lic\, a. (Chem.)
   Of, pertaining to, or designating, an acid, C4H7CO2H
   (called also methyl crotonic acid), homologous with crotonic
   acid, and obtained from croton oil (from Croton Tiglium) as
   a white crystalline substance.
   [1913 Webster]