al·ly¹ • n. / ˈalī/ (pl. -lies) a state formally cooperating with another for a military or other purpose, typically by treaty. ∎  a person or organization that cooperates with or helps another in a particular activity: he was forced to dismiss his closest political ally. ∎  (the Allies) a group of nations taking military action together, in particular the countries that fought with the U.S. in World War I and World War II.• v. / əˈlī/ (-lies, -lied) [tr.] (ally something to/with) combine or unite a resource or commodity with (another) for mutual benefit: he allied his racing experience with his father's business acumen. ∎  (ally oneself with) side with or support (someone or something): he allied himself with the rebels.al·ly² • n. (pl. -lies) variant spelling of alley² .

ally1
A. †kindred, kinsman XIV;

B. allied person or people XV. In A, — OF. alié, sb. use of pp. of alier (see next). For the loss of -é cf. ASSIGN2, etc. In B, f. next.

ally2 join as associate. XIII. — OF. alier, analogical alt. of aleier (see ALLOY).