smart alec a person considered irritating because they know a great deal or always have a clever answer to a question; the term is recorded from the mid 19th century, and is originally US.
smart bomb a radio-controlled or laser-guided bomb, often with inbuilt computer. The concept of such missiles which could home in on a target with very high levels of accuracy dates from the early 1970s, but enjoyed considerable exposure during the Gulf War of 1991.
smart money originally (in the late 17th century), money paid to sailors, soldiers, and others as compensation for disablement or injuries received while on duty or at work; smart here meant ‘physical pain’. In the modern usage of smart money, money bet or invested by people with expert knowledge, recorded from the 1920s, smart is the adjective meaning ‘quick-witted’.