(a) Not endowed with reason.
(b) Affected by loss of usual or normal mental clarity; incoherent, as from shock.
(c) Marked by a lack of accord with reason or sound judgment: an irrational dislike.
(a) Being a syllable in Greek and Latin prosody whose length does not fit the metric pattern.
(b) Being a metric foot containing such a syllable.
3. Mathematics. Of or relating to an irrational number.
Absolutely brilliant, Shoeboy. Would it have been possible for you to have selected a single, better word?