Assimilate mentally is a process of understanding and internalizing new information. The term can be broken down into two parts: assimilate, which means to absorb or take in, and mentally, which refers to the mind. The crossword solution for this term is 'DIGEST, ' which means to break down and absorb something. Digestion is a process that occurs in the body when food is broken down and absorbed into the bloodstream. In the same way, assimilating mentally involves breaking down and absorbing new information into the mind.