Mentally pooped is a term used to describe a feeling of exhaustion and mental fatigue. The two crossword solutions for this term are 'FRIED' (5 letters) and 'TOOTIREDTOTHINK' (15 letters). 'FRIED' is an informal term that means to be exhausted, while 'TOOTIREDTOTHINK' is a phrase that implies a lack of energy and motivation to think. Both terms are used to describe the same feeling of being mentally pooped.