The term 'very unusual' can be described by the crossword solutions of 'WEIRD', 'RARE', 'OUTRE' and 'onceinalifetime'. 'WEIRD' is an adjective used to describe something that is strange or bizarre. 'RARE' is an adjective used to describe something that is not common or not often seen. 'OUTRE' is an adjective used to describe something that is unconventional or extraordinary. Finally, 'onceinalifetime' is an expression used to describe something that is so special or unique that it only happens once in a lifetime. All of these words together can be used to describe something that is very unusual.