1
general::
An attempt to accomplish something by trying various means until the correct one is found. For example, The only way to solve this problem is by trial and error. The error here alludes to the failed means or attempts, which are discarded until the right way is found. [c. 1800]
American Heritage Idioms
2
general::
Phrase(s): trial and error
trying repeatedly for success. • I finally found the right key after lots of trial and error. • Sometimes trial and error is the only way to get something done.
McGrawhill's American Idioms And Phrasal Verbs