adj.
Pronunciation: i- ' ra-sh( ə -)n ə l, ˌ i(r)-
Function: adjective
Etymology: Middle English, from Latin irrationalis, from in- + rationalis rational
Date: 14th century
: not rational: as a (1) : not endowed with reason or understanding (2) : lacking usual or normal mental clarity or coherence b : not governed by or according to reason < irrational fears> c Greek & Latin prosody (1) of a syllable : having a quantity other than that required by the meter (2) of a foot : containing such a syllable d (1) : being an irrational number <an irrational root of an equation> (2) : having a numerical value that is an irrational number <a length that is irrational >
– ir · ra · tio · nal · i · ty \ - ˌ ra-sh ə - ' na-l ə -t ē \ noun
– ir · ra · tio · nal · ly \ - ' ra-sh( ə -)n ə -l ē \ adverb