1. The time when something happens or is done especially when it is thought of as having a good or bad effect on the result. 2. The ability to choose the best moment for some action, movement, etc. 3. The ability of a performer, esp. in comedy, to deliver lines, react, cut in, etc., at whatever tempo will create the desired effect. 4. The practice of investing financial assets to certain asset classes, sectors, countries, etc. to take advantage of short-term opportunities. Market timing is an active, research-based strategy vs the buy-and-hold strategy which focuses on longer timeframes.