ad. At what time; -- used interrogatively.ad. At what time; at, during, or after the time that; at or just after, the moment that; -- used relatively.ad. While; whereas; although; -- used in the manner of a conjunction to introduce a dependent adverbial sentence or clause, having a causal, conditional, or adversative relation to the principal proposition.ad. Which time; then; -- used elliptically as a noun.