A strike is the act of witholding labor in protest of conditions or wages. Jimmy Hoffa turned going on strike into an art form - using the leverage of unions to negotiate better working conditions, benefits and assigned hours for the Teamsters in the United States. A somewhat modern idea, the term came about when sailors refused to go to sea due to exceedingly poor conditions. The sailors would strike (lower) the sails while still in port - forcing the captain to either have them all shot or stock up on some tack that isn't spoiled.
'Strike' has since come to mean a general witholding of X - see tax strike, rent strike. Other examples of strikes include wildcat strike or general strike.
Also - an HTML mark-up that will 'strike out' text. This sentence, for example, is stricken. To use this tag simply place
<strike> before the text you'd like stricken and </strike> afterwards.
Also also - an adjective describing a type of aircraft which is used to attack ground targets. e.g. "The A-10 Thunderbolt is a strike aircraft."