The term 'by an eyelash' can be broken down into five crossword solutions: BAT (3 letters), MASCARA (7 letters), FLIRT (5 letters), HAIR (4 letters), and BLINK (5 letters). The word BAT refers to a small, nocturnal mammal with wings that is capable of flight. MASCARA is a cosmetic product used to darken, thicken, lengthen, and define the eyelashes. FLIRT is an act of expressing romantic or sexual interest in someone. HAIR is a filamentous biomaterial that grows from follicles found in the dermis. Finally, BLINK is a reflexive action of closing and opening the eyes quickly.