grade has 16 distinct synonyms spread across 9 of its 13 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.
a relative position or degree of value in a graded group
“lumber of the highest grade”
a number or letter indicating quality (especially of a student's performance)
“she made good marks in algebra”
the height of the ground on which something stands
“the base of the tower was below grade”
a variety of cattle produced by crossbreeding with a superior breed
Synonyms, antonyms and the broader and narrower relations for grade come from Princeton University’s WordNet. Full sources and licences.
determine the grade of or assign a grade to