What does "bitter orange" mean?

A citrus tree of the species Citrus ×aurantium, also called Citrus aurantium.

Bitter orange

Common synonyms include: bigarade, bitter orange tree, citrus aurantium, marmalade orange, seville, seville orange.

noun

noun ·Rare ·Advanced level

Noun

1
A citrus tree of the species Citrus ×aurantium, also called Citrus aurantium. countable, uncountable
2
highly acidic orange used especially in marmalade wordnet
3
A citrus tree of the species Citrus limetta. countable, uncountable
4
any of various common orange trees yielding sour or bitter fruit; used as grafting stock wordnet
5
The fruit of these species. countable, uncountable