A somewhat literary or formal expression for a bed where one lies ill. Often used in contexts of illness, convalescence, or death.
See also: 病床
彼は病の床で遺言を書いた。
He wrote his will from his sickbed.
Compound of 病 (yamai, 'illness') + の (no, possessive particle) + 床 (toko, 'bed'). The expression is transparent and follows a common pattern for forming noun phrases.