Clear ice

From Glossary of Meteorology

clear ice

(Or clear icing.) Smooth compact rime, usually transparent, fairly amorphous, with a ragged surface, and morphologically resembling glaze.

This term has two different major applications. 1) Most commonly, it is used as a synonym for glaze, particularly with respect to aircraft icing. Factors that favor clear ice (or glaze) formation are large drop size, rapid accretion of liquid water, slight supercooling, and slow dissipation of latent heat of fusion. Thus, an aircraft flight through supercooled rain at an air temperature of 0° to -4°C is most conducive to clear icing. This type of icing does not seriously distort airfoil shape, but it does add appreciably to the weight of the craft. 2) The term may also be applied to homogeneous bodies of glacier ice and lake ice.
Compare rime ice.