Definition of tachy:
(n) :
(medicine, colloquial) Tachycardia.
(adj) :
(medicine, colloquial) Tachycardic.
(n) :
(medicine, colloquial) Tachypnoea.
(adj) :
(obsolete) Alternative form of tetchy. [(UK, Ireland, Commonwealth, Southern US) Synonym of touchy: easily annoyed or irritated, peevish, testy, irascible; also (figurative) extremely sensitive, difficult to manage, use, or work.]