⇨ L7; l-sevennoun a staid person who is uninterested in or unsympathetic to the fashionable interests of teenagers. The shapes of L and 7 can combine to form a SQUARE (a conventional person). This slang may be entirely gestural in expression: the forefinger and thumb on each hand extended at right angles, left (L) and right (7) combining to make the shape of a square US, 1956