Adjournment has two separate meanings. Depending on how it is used, it can either mean "conclude" a meeting or temporarily "suspend" a meeting.

#1 Conclude a Meeting. To adjourn a meeting is to terminate or finish a meeting.

When the business for which the . . . meeting was called has . . . been completed and no question is pending, someone should move "to adjourn," or the chair can call for such a motion. (Robert's Rules, 10th ed., p. 535.)

#2 Continue to a Later Date. Where the business of the meeting is not finished, a meeting may be adjourned to a later date so as to continue with the meeting's business. This often occurs when an association fails to achieve quorum at an annual meeting and their bylaws allow the membership to adjourn the meeting to a later date.

The only action that can legally be taken in the absence of a quorum is to fix the time to which to adjourn, recess, or take measures to obtain a quorum. . . . If a quorum cannot be obtained, the chair calls the meeting to order, announces the absence of a quorum, and entertains a motion to adjourn [to a later date]. (Robert's Rules, 10th ed., pp. 336-338.)