The word "tetched" refers to someone who is irrational, eccentric or slightly crazy. There are many synonyms for this term that can be used to describe a person who appears to be mentally unbalanced. Some popular synonyms for "tetched" include unhinged, deranged, nuts, batty, loony, insane, lunatic, wacky, bonkers, and cuckoo. Each of these words can convey a different shade of meaning and may be more or less appropriate depending on the context. Regardless of the specific synonym chosen, the common thread is that each term describes someone who is somewhat unbalanced or unstable in their behavior or thinking.