動詞 retroflex:

1. bend or turn backward
   同義詞：replicate
2. articulate (a consonant) with the tongue curled back against the palate

形容詞 retroflex:

1. bent or curved backward
   同義詞：retroflexed
2. pronounced with the tip of the tongue turned back toward the hard palate
   同義詞：cacuminal

ret.ro.flex

adj.also （形容詞） 也作
retroflexed
Bent, curved, or turned backward.
后折的，后彎的，或向后轉(zhuǎn)的
Linguistics Pronounced with the tip of the tongue turned back against the roof of the mouth.
【語言學】 卷舌音的：將舌尖向后卷抵住口中硬腭而發(fā)音的
n.（名詞）
Linguistics A sound pronounced with the tongue in retroflex position, as the sound (r) in some varieties of English.
【語言學】 卷舌音：舌尖處于卷舌音狀態(tài)時發(fā)出的聲音，如英語的一些變種音(r)

來源：
Latin *retrôflexus [past participle of] retrôflectere [to bend back]
拉丁語 *retrôflexus [] retrôflectere的過去分詞 [向后彎]
retrô [retro-]
retrô [表示.向后.]
flectere [to bend]
flectere [彎曲]

【引伸】
ret.roflex.ion 或
ret.roflec.tion
n.（名詞）