The term 'FIRM IN SHAPE' can be summarized as a SOLID structure that is in good condition. The crossword solution for this term is 'SOLID', which is a five-letter word that describes something that is strong and stable. This term is often used to describe something that is not easily broken or damaged, and is also used to refer to something that is reliable and dependable. In the context of physical fitness, it can also refer to having a body that is toned and in good shape.