Definition of preempting:
(v) :
(transitive) To prevent or beat to the punch, to forestall an expected occurrence by acting first.
(v) :
(transitive) To displace or take the place of (by having higher precedence, etc).
(v) :
(transitive) To appropriate first.
(v) :
(transitive) To secure (land, etc.) by the right of preemption (purchasing before others, e.g. land because one already occupies it).
(v) :
(bridge, intransitive) To make a preemptive bid at bridge.
(n) :
(bridge) A preemptive bid.