Rahu

Rahu is the ascending lunar node. In Hindu mythology, Rahu is a snake that swallows the sun or the moon causing eclipses. He is depicted in art as a dragon with no body riding a chariot drawn by eight black horses.According to legend, during the Samudra manthan, the asura Rahu drank some of the divine nectar. But before the nectar could pass his throat, Mohini (the female avatar of Vishnu) cut off his head. The head, however, remained immortal. It is believed that this immortal head occasionally swallows the sun or the moon, causing eclipses. Then, the sun or moon passes through the opening at the neck, ending the eclipse.
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Noun
1. a demon who swallows the sun causing eclipses
(hypernym) Hindu deity

[Hindu] In Hindu myth, Rahu is demon that causes eclipses. He rides a chariot pulled by eight black horses, with his mouth wide open, ready to devour the sun or moon. If he succeeds, a solar or lunar eclipse will follow. He is usually portrayed as a dragon's head, without a body. In Tibet he is the Buddhistic lord of the nine planets, and one of the Krodhadevatas (terror-inspiring gods). There he is portrayed with nine heads and the body of a snake.

Rahu (Sanskrit) The seizer; a daitya supposed to seize the sun and moon and thus cause eclipses. "A giant, a Demi-god, the lower part of whose body ended in a Dragon or Serpent's tail. During the churning of the Ocean, when the gods produced amrita -- the water of Immortality -- he stole some of it, and drinking, became immortal. The Sun and Moon, who had detected him in his theft, denounced him to Vishnu, who placed him in the stellar spheres, the upper portion of his body representing the Dragon's head and the lower (Ketu) the Dragon's tail; the two being the ascending and descending nodes. Since then, Rahu wreaks his vengeance on the Sun and Moon by occasionally swallowing them. But this fable had another mystic meaning, since Rahu, the Dragon's head, played a prominent part in the mysteries of the Sun's (Vikarttana's) initiation, when the candidate and the Dragon had a supreme fight" (SD 2:381).

k.o. monster that causes lunar eclipses by swallowing moon