Euphorbia degeneri is a subshrub with prostrate to decumbent stems measuring 0.05–0.4 m in length. The stems are nodose, often tortuous and gnarled, and range from pilose to villous. Flowering branches are 1–1.5 mm in diameter. The leaves are simple and opposite, arranged distichously. The blades are orbicular or elliptic to reniform, 5–20(–25) mm long and 5–15(–25) mm wide. The apex is rounded to obtuse, sometimes retuse or mucronulate, and the base is cordate. The surfaces can be glabrous, pubescent at the basal margin, pilose, or glaucous. Margins are entire; the petioles are 0.5–1 mm long and villous. Stipules are rounded–triangular, 1–2 mm long, and can be glabrous or villous, erose, and ciliate. The flowers are in cyathia, primarily solitary at the ends of the branches, with peduncles 0.5–1 mm long and pilose to villous. The involucre is campanulate, 1.5–2 mm high and wide, glabrous to pilose, with four green, glabrous to pilose, unappendaged glands. Flowers are unisexual and highly reduced. Pistillate flowers are solitary on a gynophore, while staminate flowers are in 5 groups or cymules, each with 1 to several flowers. Both the calyx (sepals) and corolla (petals) are absent. Male flowers are reduced to a single stamen with articulation at the junction of the pedicel and filament, subtended by slender bracteoles. The ovary is superior, with green to white styles, bifid ½ their length, 0.5–1 mm long, and sparsely pubescent, with slightly thickened stigmas. The fruit consists of green capsules (1.5–)2–2.5 mm long, glabrate to pilose, with recurved gynophores that are exserted 1.5–2 mm from the involucre and are pilose or rarely glabrous. Seeds are white, 1.7–1.8 mm long, and rugose. It occurs in coastal and strand vegetation at 0-50 meters.