1. Med. A dark-colored liquid medicine, chiefly composed of opium, with vinegar and spices.
1823. Byron, Juan, IX. lxvii. A quintessential laudanum or ‘black drop.’
1878. Cycl. Med., XVII. 844. Black drops, Godfrey’s Elixir … etc. all contain opium.
2. Astron. A dark drop-like appearance observed at solar transits of Venus and Mercury immediately after apparent internal contact at ingress, and before it at egress, giving to the planet a pear-shaped appearance, elongated towards the sun’s edge.
1869. E. Dunkin, Midn. Sky, 252. The formation of the black-drop … was very clearly observed at … Greenwich.
1878. Newcomb, Pop. Astron., II. iii. 189. Father Hell’s black drop, seen before the limbs [of Sun and Venus] were in contact.
