壑 is a deep gully or ravine, mostly in 沟壑 (gullies). The idiom 欲壑难填 — 'the ravine of desire is hard to fill' — uses it as a metaphor for insatiable greed.
Components
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壑hè
deep ravine in the earth
A compound meaning-graph: a complex upper element depicting a deeply eroded watercourse sits over the earth radical 土 at the bottom, together picturing a gully carved into the ground. The intricate top has no independent standalone reading, so the character is treated as one unit. Indexed under the earth radical by tradition.
Filed under radical 土 (tǔ) by convention. 土 is not a separate component in 壑, so no strokes are highlighted.
