Full Idea
The idea of basic emotions is that our concepts of emotions are hierarchically organised. For example, if anger is a basic emotion, then less basic species of anger might be annoyance, fury, rage, indignation, and so forth.
Gist of Idea
A basic emotion is the foundation of a hierarchy, such as anger for types of annoyance
Source
Peter Goldie (The Emotions [2000], 4 'Evidence')
Book Reference
Goldie,Peter: 'The Emotions' [OUP 2002], p.87
A Reaction
Most modern theorists seem to reject this idea. In a family of related emotions (each having a similar focal object), it is hard to see which one of them is basic, other than being the best known. Maybe the weakest one is basic?