The term 'MONOKINI'S LACK' can be solved by the three letter word 'BRA'. A bra, or brassiere, is a type of undergarment worn by women to support their breasts. It is typically composed of two cups and straps that go over the shoulders. The monokini is a type of swimsuit that does not include a top, leaving the wearer's breasts exposed. Therefore, the lack of a bra in a monokini is what is being referred to by the term 'MONOKINI'S LACK'.