To close a window (typically by clicking a button marked with an X symbol).
To cross out with a series of the letter X, or with scribbles or lines.
To sing a song poorly.
To put down or euthanize.
To remove data.
To exhaust duly and thus recreate or build up.
To penetrate sexually in an aggressive way.
To damage beyond use or repair.
To severely disrupt the well-being of (a person); ruin.
To defeat soundly.
To neutralize, undo a property or condition.