arcus(redirected from arcus senilis)
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Related to arcus senilis: arcus juvenilis, corneal arcus
A dense and horizontal roll-shaped accessory cloud, with more or less tattered edges, situated on the lower front part of the main cloud.
A low, horizontal cloud formation associated with the leading edge of thunderstorm outflow (i.e., gust front). Roll clouds and shelf clouds are both types of arcus clouds.