Sanskrit शुक्र alternately romanized as sukra, Çukra, etc.
Literally means, "semen, sperm, white, spotless, pure, gold, juice, clear, brightness, bright, Venus, Friday."
Meaning "bright," in scriptures shukra often refers to the Sun.
In yoga and tantra, shukra refers to the solar, masculine aspect of the sexual energy, the complement of the feminine, lunar aspect, called by various names such as rajas or manthin (the Moon).
"The Shukra and Manthin (grahas), forsooth, are his eyes. Now the Shukra, indeed, is he that burns yonder (the sun); and because it burns there therefore it is (called) Shukra ('bright'). And the Manthin, indeed, is the moon. He mixes it with (barley) meal: thus he makes it to be gruel (mantha), whence it is (called) Manthin. Now those two (sun and moon); forsooth, are the eyes of these creatures; for were those two not to rise, these (creatures) could not distinguish even their own hands. One of them is the eater, and the other the food to wit, the Shukra is the eater, and the Manthin the food. To one of them corresponds the eater, and to the other the food; to wit, the eater corresponds to the Shukra, and the food to the Manthin." -Satapatha Brahmana, Second Adhyâya. First Brâhmana
"He for whom knowing thus these Shukra and Manthin (cups) are drawn, prospers himself, his foe is defeated... The Shukra is yonder sun, the Manthin is the moon... 'Engendering heroic off spring), come forth, Shukra, with pure radiance', 'Engendering prolific offspring, come forth, Manthin, with mixed radiance..." -Yajur Veda, Kanda 4
"The yogis who practice Oordhavareta Yoga (positive Sexual Magic) do not ejaculate their ens seminis. Through this way, the combination of shukra (solar atoms) and rajas (lunar atoms) is performed within the philosophical egg, in other words, within the very sexual laboratory of the alchemist." - Samael Aun Weor, Alchemy and Kabbalah in the Tarot