tackle has 8 distinct synonyms spread across 4 of its 8 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
the person who plays that position on a football team
“the right tackle is a straight A student”
(American football) a position on the line of scrimmage
“it takes a big man to play tackle”
(American football) grasping an opposing player with the intention of stopping by throwing to the ground
Synonyms, antonyms and the broader and narrower relations for tackle come from Princeton University’s WordNet. Full sources and licences.
seize and throw down an opponent player, who usually carries the ball