⇨ lude; ludnoun a tablet of the recreational drug methaqualone, best known as Quaaludes™ or, in a manner not inconsistent with the imprecision of the drug culture, any central nervous system depressant. Quaalude™ was a brand name for methaqualone, a muscle relaxant and barbiturate substitute introduced in 1965 and made illegal in the US in 1984 US, 1973