vipakkhika : [adj.] siding with the enemy.

A.P. Buddhadatta Mahathera, Concise Pali-English and English-Pali Dictionary [available as digital version from Metta Net, Sri Lanka]

Vipakkhika (adj.) [vipakkha+ika] 1. [vi+pakkha1 1] without wings J i.429. -- 2. [vi+pakkha1 2] opposite, hostile Sdhp 71.

Pali-English Dictionary, TW Rhys Davids, William Stede,