When someone bites off more than they can chew, it means they have taken on more than they can handle or manage. The phrase is often used to indicate that someone has taken on a task that is too difficult or complex for them to complete successfully. Some synonyms for "bite off more than can chew" include overreach, overextend, overcommit, overburden, overwhelm, overtax, exhaust, and strain. All of these words describe the act of taking on more than one can handle or manage. It is important to recognize the limits of one's abilities and capacities to avoid biting off more than they can chew and facing failure or burnout.