Wordnet 3.0
NOUN (2)
1. 
 a native or inhabitant of Parthia; 
2. 
 the Iranian language spoken in the Parthian kingdom (250 BC to AD 226); 
ADJECTIVE (1)
1. 
 pertaining to Parthia or its people or language or culture; 
- Example: "Parthian archeology"
The Collaborative International Dictionary of English v.0.48:
Parthian \Par"thi*an\, a.
   Of or pertaining to ancient Parthia, in Asia. -- n. A native
   of Parthia.
   [1913 Webster]
   Parthian arrow, an arrow discharged at an enemy when
      retreating from him, as was the custom of the ancient
      Parthians; hence, a parting shot.
      [1913 Webster]
WordNet (r) 3.0 (2006):
Parthian
    adj 1: pertaining to Parthia or its people or language or
           culture; "Parthian archeology"
    n 1: a native or inhabitant of Parthia
    2: the Iranian language spoken in the Parthian kingdom (250 BC
       to AD 226)