talking dictionary
n.— «A few British bachelors developed liaisons with local lasses, usually tea-pickers. Such women were euphemistically—and imaginatively—called “talking dictionaries.” For she also helped to brush up the man’s knowledge of Tamil—a prerequisite then, as now, for advancement in a planter’s career.» —“Tea-time tricks” by George N. Netto Indian Express (Mumbai) June 14, 2005. (source: Double-Tongued Dictionary)