The term 'hard to explain' can be described by the following crossword solutions: ODD (3 letters), WEIRD (5 letters), BIZARRE (7 letters), EERIE (5 letters), and STRANGE (7 letters). These words all refer to something that is not easily understood or explained, and can be used to describe a situation, object, or person. ODD implies something that is unusual or out of the ordinary, while WEIRD suggests something that is STRANGE and mysterious. BIZARRE implies something that is very STRANGE and unexpected, and EERIE implies something that is spooky or creepy. Finally, STRANGE implies something that is unfamiliar or unfamiliar in a way that is difficult to explain.