Longman Dictionary of Contemporary English
Wiktionary
n. (context grammar English) A subordinate clause.
WordNet
n. a clause in a complex sentence that cannot stand alone as a complete sentence and that functions within the sentence as a noun or adjective or adverb [syn: subordinate clause]
Wikipedia
A dependent clause is a clause that provides an independent clause with additional information, but which cannot stand alone as a sentence. Dependent clauses either modify the independent clause of a sentence or serve as a component of it. Some grammarians use the term subordinate clause as a synonym for dependent clause. Others use subordinate clause to refer only to adverbial dependent clauses.
The different types of dependent clauses include noun clauses, relative (adjectival) clauses, and adverbial clauses.