【Recoil】 ,  【shrink】 ,  【flinch】 ,  【wince】 ,  【blench】 ,  【quail】  can all mean to draw back from something, usually through fear, faintheartedness, or disgust.

【Recoil】 more than any of the succeeding terms suggests the physical signs of such drawing back or the sensations that accompany it. The term may imply a start or a sudden movement away, but often the term suggests an inner or not outwardly apparent shaking or stirring that affects one mentally more than physically.

【Shrink】 implies an instinctive 【recoil】 (as from something painful or unpleasant or horrible); it often implies cowardice, but it may imply extreme sensitiveness or scrupulousness.

【Flinch】 implies a failure in resolution or an inability to overcome one’s desire to avoid or evade something that is painful, difficult, or abhorrent.

【Flinch】  is sometimes used but  【wince】 more often when by some involuntary, often slight, physical movement (as starting or recoiling) one manifests pain, fear, disgust, or acute sensitiveness.

【Blench】  may be indistinguishable from  【flinch】 ; it often, however, carries a stronger suggestion of faintheartedness or of signs of fear.

To  【quail】 is to 【shrink】 coweringly, as from something which strikes terror.