The term 'being of questionable authenticity' can be described by the crossword solutions APOCRYPHAL (10 letters), LEER (4 letters), IFFY (4 letters) and SHADY (5 letters). APOCRYPHAL means something that is of doubtful authenticity or origin, while LEER means to look at someone with a sly or suspicious expression. IFFY is an informal word meaning uncertain or questionable, and SHADY is a slang term for something that is not honest or trustworthy. All of these words describe something that is not certain or reliable.