noun [usuallysing.]
1 a play, concert, etc. for which all the tickets have been sold:
Next week's final looks like being a sell-out. * a sell-out tour
2 a situation in which sb betrays a person or group who trusted them, by not doing sth that they promised to do, or by doing sth that they promised not to do:
The workers see the deal as a union sell-out to management.
