1
general::
In addition to the required amount. For example, Whenever she bakes she adds a little more cinnamon for good measure, or He didn't argue with my price, so I gave him some extra supplies for good measure.
American Heritage Idioms
2
general::
Phrase(s): for good measure
as extra; (adding) a little more to make sure there is enough. • When I bought a pound of nails, the clerk threw in a few extra nails for good measure. • I always put a little extra salt in the soup for good measure.
McGrawhill's American Idioms And Phrasal Verbs