Black washBlack" wash`\or Blackwash \Black"wash\, n. 1. (Med.) A lotion made by mixing calomel and lime water. 2. A wash that blackens, as opposed to whitewash; hence, figuratively, calumny. To remove as far as he can the modern layers of black wash, and let the man himself, fair or foul, be seen. --C. Kingsley.