1.Definition: coming from the outside
"Extraneous light in the camera spoiled the photograph", "Relying upon an extraneous income"
2.Definition: not belonging to that in which it is contained; introduced from an outside source
"Water free of extraneous matter"
3.Definition: not essential
"The ballet struck me as extraneous and somewhat out of keeping with the rest of the play"
4.Definition: not pertinent to the matter under consideration
"An issue extraneous to the debate"