Adjective: protrusible prow'troo-su-bul or prow'troo-zu-bul [N. Amer], pru'troo-si-bul or pru'troo-zi-bul [Brit]- Capable of being thrust forward, as the tongue
"The chameleon's protrusible tongue can extend to twice its body length";
- protrusile
See also: extensible, extensile