What is the meaning of ᛁ?

A letter of the Runic alphabet, present in the Elder Fuþark (ᛁ), the Anglo-Saxon Fuþorc (ᛁ, called is), and the Younger Fuþark (ᛁ, called isa in Old Norse and iss in Icelandic), representing /i/ or /iː/ and associated with ice.

the eleventh letter of the Old English runic alphabet, representing /i/ and pronounced īs (“ice”)

Source: wiktionary.org