Logically sound is a term used to describe an argument or statement that is well-reasoned and based on evidence. The two crossword solutions for this term are 'SOLID' and 'VALID'. SOLID implies that the argument is strong and reliable, while VALID suggests that it is based on facts and has logical reasoning. Therefore, logically sound can be described as an argument or statement that is both strong and reliable, as well as based on facts and logical reasoning.