compound sentence

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

• noun A sentence of two or more coordinate independent clauses, often joined by a conjunction or conjunctions, as The problem was difficult, but I finally found the answer.

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

• noun grammar a sentence that has two or more independent clauses, joined by a conjunction (such as 'but', 'and') and/or punctuation (such as ','). Compare simple sentence.

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

• noun a sentence composed of at least two coordinate independent clauses