The crossword solution for the term BIRD MISCHIEVOUS is ARCH, which is a four-letter word. An ARCH is a curved structure that is used to span an opening and support the weight above it. In architecture, arches are often used to create doorways or windows. The term 'bird mischievous' could refer to a bird that is playful and likes to cause trouble. This could be a bird that steals food from other birds or one that likes to play pranks on people.