View Full Document. Ice Pellets Ice pellets (also called sleet) are refrozen snowflakes. They occur when a layer of air aloft is warm enough (> 0 ï° C) to melt snowflakes into raindrops but the air near the ground is cold enough to freeze the drops.
acarid - very small free-living arachnid that is parasitic on animals or plants; related to ticks. 1  mite - any of numerous very small to minute arachnids often infesting animals or plants or stored foods. 2  Acaridae, family Acaridae - mites.
afferent pupillary defect. Afferent Pupillary Defect (APD) or Marcus-Gunn pupil is a condition of the eye where the pupil doesn't dilate appropriately to the level of light reaching it.This will often result in one pupil appearing larger than the other (relative afferent pupillary defect-RAPD).This person with APD is often unaware of it except by looking in a mirror. There are many causes of APD including Optic Neuritis (ON) , glaucoma and optic nerve tumor.his will often result in one pupil appearing larger than the other (relative afferent pupillary defect-RAPD). This person with APD is often unaware of it except by looking in a mirror. There are many causes of APD including Optic Neuritis (ON) , glaucoma and optic nerve tumor.