Definition of megalomania
1
: a mania (see mania sense 2a) for great or grandiose performance
an outburst of wildly extravagant commercial megalomania — The Times Literary Supplement (London)
2
: a delusional mental illness that is marked by feelings of personal omnipotence and grandeur
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Merriam-Webster unabridged
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Time Traveler for megalomania
The first known use of megalomania was in 1885
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