Spongy ice

From Glossary of Meteorology

spongy ice

Ice that contains liquid water; a composite of ice and liquid water.

Spongy ice is a form of accretion of supercooled drops in which the heat transfer is inadequate to freeze all the water. The excess water is included within the growing ice. Spongy ice may also form during the melting of low-density accretions by the meltwater soaking into the pores.