top has 33 distinct synonyms spread across 14 of its 22 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. Its 2 recorded opposites are bottom, side.
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 top or extreme point of something (usually a mountain or hill)
“the view from the peak was magnificent”
the first half of an inning; while the visiting team is at bat
“a relief pitcher took over in the top of the fifth”
the greatest possible intensity
“he screamed at the top of his lungs”
platform surrounding the head of a lower mast
a conical child's plaything tapering to a steel point on which it can be made to spin
“he got a bright red top and string for his birthday”
a garment (especially for women) that extends from the shoulders to the waist or hips
“he stared as she buttoned her top”
a canvas tent to house the audience at a circus performance
“he was afraid of a fire in the circus tent”
be at the top of or constitute the top or highest point
“A star tops the Christmas Tree”
reach or ascend the top of
“The hikers topped the mountain just before noon”
strike (the top part of a ball in golf, baseball, or pool) giving it a forward spin
Synonyms, antonyms and the broader and narrower relations for top come from Princeton University’s WordNet. Full sources and licences.