/si rak"/ ; Fr. /say rddannk"/ , n. , pl. séracs /-raks"/ ; Fr. /-rddannk"/ .
a large irregularity of glacial ice, as a pinnacle found in glacial crevasses and formed by melting or movement of the ice.
Also, serac .
[ 1855-60; sérac kind of white cheese (cf. ML seracium ), ult. serum whey ]