Nouns

(n)offside(sport) the mistake of occupying an illegal position on the playing field (in football, soccer, ice hockey, field hockey, etc.)

Adjectives

(a)offside, offsidesillegally beyond a prescribed line or area or ahead of the ball or puck“the touchdown was nullified because the left tackle was offside”

Adverbs

(r)offsideillegally in advance of the ball or puck