Definitions
1.VerbTo appropriate first."He preempted that hill to be its king."
2.VerbTo displace or take the place of (by having higher precedence, etc)."Floppy disks were preempted by CDs."
3.VerbTo prevent or beat to the punch, to forestall an expected occurrence by acting first.
4.VerbTo secure (land, etc.) by the right of preemption (purchasing before others, e.g. land because one already occupies it).
5.VerbTo make a preemptive bid at bridge.
6.NounA preemptive bid.