From WordNet (r) 3.0 (2006) [wn]:
presidential
adj 1: relating to a president or presidency; "presidential
aides"; "presidential veto"
2: befitting a president; "criticized the candidate for not
looking presidential" [ant: unpresidential]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Presidential \Pres`i*den"tial\, a.
1. Presiding or watching over. "Presidential angels."
--Glanvill.
[1913 Webster]
2. Of or pertaining to a president; as, the presidential
chair; a presidential election.
[1913 Webster]