Barely perceptible is an adjective used to describe something that is very difficult to detect or observe. It can be broken down into five crossword solutions: WEE (3 letters), FAINT (5 letters), TINY (4 letters), SUBTLE (6 letters), and LIMINAL (7 letters). WEE means very small, FAINT implies something that is barely audible or visible, TINY suggests something that is extremely small, SUBTLE implies something that is not easily noticed, and LIMINAL refers to something that is on the threshold of being perceived. Together, these words create a phrase that describes something that is almost impossible to detect.