Webster's English Dictionary

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intrusion

in.tru.sion \in-'tru:-zh*n\ n [ME, fr. MF, fr. ML intrusion-, intrusio, fr. 
   L intrusus, pp.] of intrudere 1: the act of intruding or the state of being 
   intruded; specif : th e act of wrongfully entering upon, seizing, or taking 
   possession of the property of another 2: the forcible entry of molten rock 
   or magma into or between other rock fo rmations; also : the intruded magma