tachyphylaxis
noun
tachy·phy·lax·is
| \ ˌtak-i-fi-ˈlak-səs
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plural tachyphylaxes\ -ˌsēz
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Medical Definition of tachyphylaxis
: diminished response to later increments in a sequence of applications of a physiologically active substance (as the diminished pressor response that follows repeated injections of renin)