Sometimes — and only sometimes — a YouTube video is worth a thousand words.
1. [NO OBJECT] (Of cows and certain other large animals) give birth to a calf.
2. [WITH OBJECT] (Of an iceberg or glacier) split and shed (a smaller mass of ice).
2.1 [NO OBJECT] (Of a mass of ice) split off from an iceberg or glacier.
Old English cealfian, from cealf “calf”. Of icebergs, 1837. (Etymonline)