Crossword clue: a closed plane curve resulting from the intersection of a circular cone and a plane cutting completely through it

The most common answer is ellipse (7 letters).

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

Possible answers

ellipse 7 letters wn-def

a closed plane curve resulting from the intersection of a circular cone and a plane cutting completely through it

oval 4 letters wn-def

a closed plane curve resulting from the intersection of a circular cone and a plane cutting completely through it