A low, horizontal tube-shaped arcus cloud associated with a thunderstorm gust front (or sometimes with a cold front). Roll clouds are relatively rare; they are completely detached from the thunderstorm base or other cloud features, thus differentiating them from the more familiar shelf clouds. Roll clouds usually appear to be 'rolling' about a horizontal axis, but should not be confused with funnel clouds.
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Sexual Intercour...
Roentgen Equivalent Man
Roll-on/Roll-off Container Ship
