clasp knife

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

• noun A pocketknife with a folding blade.

from The Century Dictionary.

• noun A knife with one or more blades which fold into the handle.
• noun In a narrower sense, a large knife with one blade which folds into the handle and may be locked when open by a catch on the back.

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

• noun Alternative spelling of clasp-knife.

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

• noun a large knife with one or more folding blades