Mistborn is a fantasy book about people with magical abilities called allomancers.
Allomancers "burn" (metabolize metals in the body for magical powers) ingested metals, thereby enhancing various physical and mental capacities.
An nicrosil allomancer is referred to as a Nicroburst. An Allomancer while burning nicrosil can cause a target Allomancer currently burning metals to burn them in a brief, intense flash. This is similar to duralumin, which targets the Allomancer's internal metals, while nicrosil is an external metal (targeting other Allomancers).