From Longman Dictionary of Contemporary Englishslide ruleˈslide rule noun [countable] HMan old-fashioned instrument used for calculating numbers, that looks like a ruler and has a middle part that slides across
Examples from the Corpus
slide rule• All of them will make either a slide rule or an abacus as a way of presenting how number sets work.• There were several colors of pencils, even a slide rule, at which she was frowning.• They are not activities which can be accomplished with a slide rule or computer or calculator.• Greatly skilled at plotting the heavens and working things out on the old slide rule.• The slide rule, the calculating machine, and the computer are the enemies of the arithmetic mind. 