transform fault

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

• noun A strike-slip fault, common in mid-ocean ridge regions, in which there has been a sudden change in the form or direction of displacement.

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

• noun geology A geological fault (a form of strike-slip fault) found in mid-ocean ridges in which displacement undergoes a sudden change in direction