Example : An issue extraneous to the debate.
The price was immaterial.
Mentioned several impertinent facts before finally coming to the point.

Synonyms : immaterial, impertinent, orthogonal

Example : The ballet struck me as extraneous and somewhat out of keeping with the rest of the play.

Example : Water free of extraneous matter.
Foreign particles in milk.

Synonyms : foreign

Example : Extraneous light in the camera spoiled the photograph.
Relying upon an extraneous income.
Disdaining outside pressure groups.

Synonyms : external, outside