底てい角かくていかくMeanings1nounbase anglemathematicsIn geometry, the angle formed by the base and one of the legs of an isosceles triangle, or more generally the angle adjacent to the base of a figure.二に等とう辺へん三さん角かく形けいの底てい角かくは等ひとしい。The base angles of an isosceles triangle are equal.