adj.
 (hardier, hardiest)
 capable of enduring difficult conditions; robust. 
▸(of a plant) able to survive outside during winter.
 
  Derivative
  
    - hardily adv.
  - hardiness n.
 
   
  Etymology
  ME: from OFr. hardi, past part. of hardir ‘become bold’, of Gmc origin; rel. to hard.