The antonym for "over-topping" is "under-topping." "Over-topping" refers to exceeding the highest point or exceeding a limit, while "under-topping" means not reaching or falling short of the highest point or limit. For instance, if a tree is towering over other trees and is the tallest in the forest, it is over-topping the rest of the trees. On the contrary, if a tree is shorter than the surrounding trees and doesn't reach the highest point, it is under-topping other trees. Similarly, if a person's expenses exceed their income, they are over-topping their budget. Conversely, if their expenses are lower than their income, they are under-topping their budget.