means The sensation of needing or craving something to drink, especially water — and, by extension, an intense longing for anything you lack.

from From Old English 'thurst' (the noun) and 'thyrstan' (the verb), tracing back to Proto-Germanic '*thurstuz' — a cousin of German 'Durst' and Dutch 'dorst.' The deeper root is the Proto-Indo-European '*ters-,' meaning 'to dry,' which also gives us the parched-earth words 'terrain' and 'torrid.' So thirst is, at its bones, the feeling of going dry. The figurative sense — 'a thirst for knowledge,' 'a thirst for revenge' — has been with English for centuries; the slangy 'thirsty' meaning desperate for attention is a much more recent flowering of the same dry-mouthed metaphor.