1 : to arrange things so that they form a line or are in proper position
(+ object)
The storekeeper carefully aligned (=lined up) the cans on the shelf.
He aligned the two holes so he could put the screw through them.
The text is aligned (=in line) with the bottom of the picture.
The two parts of the machine are not properly aligned.
(no object)
The two parts of the machine don’t align (=line up) properly.
The text aligns with the bottom of the picture.
2 : (+ object) : to change (something) so that it agrees with or matches something else
The schools had to align their programs with state requirements.
3 : to join a group that is supporting or opposing something
(+ object)
He has aligned himself with the protesters. (=he has joined the protesters)
(no object)
She is aligning with other senators to oppose his nomination.