LESS THAN SOLID can be described as something that is not stable or reliable. The crossword solutions for this term are TWOD (4 letters), THAWING (7 letters), and IFFY (4 letters). TWOD stands for two dimensional, which means something that is flat and has no depth. THAWING means to become less rigid or frozen, which implies that something is not solid. Lastly, IFFY means uncertain or unreliable, which further reinforces the idea that something is not solid.