#1 retroflex v. [replicate] bend or turn backward. wn
#2 retroflex s. [retroflexed] bent or curved backward. wn
#3 retroflex v. articulate (a consonant) with the tongue curled back against the palate; "Indian accents can be characterized by the fact that speakers retroflex their consonants". wn
#4 retroflex s. [cacuminal] pronounced with the tip of the tongue turned back toward the hard palate. wn
vizzz