coordinating conjunction

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A conjunction that connects two identically constructed or syntactically equal grammatical elements, such as or in They don't know whether they're coming or going.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun grammar A conjunction that joins two grammatical elements of the same status or construction.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the coordination by conjunction of linguistic units of the same status
• noun a conjunction (like `and' or `or') that connects two identically constructed grammatical constituents