Longman Dictionary English From Longman Dictionary of Contemporary EnglishRelated topics: Mathsisosceles trianglei‧sos‧ce‧les tri‧an‧gle /aɪˌsɒsəliːz ˈtraɪæŋɡəl $ -ˌsɑː-/ noun [countable] technical HMa triangle in which two of the sides are the same length → equilateral triangle ldoceonline.com