ˈshlirən noun plural
Etymology: German, from German dialect schlieren, plural of schlier, literally, ulcer, from Middle High German slier, sliere; probably akin to Middle High German slier mud — more at slur
1. : small masses or streaks that differ in mineral composition from the main body of an igneous rock but graduate insensibly into it
2. : regions or streaks in a transparent medium (as a fluid) that have a density and hence a refractive index differing from that of the bulk of the medium and often resulting from pressure or temperature differences and that are detected especially by photographing the passage of a beam of light (as in the shock waves of a projectile)
• schlie·ric -rik adjective