kāsu : [f.] pit.

A.P. Buddhadatta Mahathera, Concise Pali-English and English-Pali Dictionary [available as digital version from Metta Net, Sri Lanka]

Kāsu [cp. Sk. karṣū, fr. kṛṣ] a hole; only in cpd. angāra- kāsu a cinderhole, a fire -- pit, usually understood as a pit of glowing cinders J i.232. Mostly found in similes, e. g. S iv.56, 188; Sn 396; Sdhp. 208; and in kāmā angārakās' ûpamā metaphor A iv.224=v.175; see also kāma.

Pali-English Dictionary, TW Rhys Davids, William Stede,