What is Adjournment Sine Die?

Legal Definition
Adjournment sine die (from the Latin "without day") means "without assigning a day for a further meeting or hearing". To adjourn an assembly sine die is to adjourn it for an indefinite period. A legislative body adjourns sine die when it adjourns without appointing a day on which to appear or assemble again.

It can be used in reference to United States legislatures whose terms or mandates are coming to an end, and it is anticipated that this particular body will not meet again in its present session, form, or membership. A legislative body adjourned in this way may be called back into special session, a reason why sine die adjournment rather than dissolution may be preferred in some cases.

A corporate board might adjourn sine die if the corporation were being sold, merged, or liquidated.

A convention or a series of mass meetings would adjourn sine die if the business of these meetings has been completed. In these cases, the adjournment dissolves the body.

A court may also adjourn a matter sine die, which means the matter is stayed until further notice. This may be due to various reasons. For example, if the case is started with a wrong procedure chosen, the judge may adjourn the matter sine die, so that the party may choose to start the action again with the correct procedure. It may also be thus adjourned if there is no possibility of proceeding in the foreseeable future—for example, an action may be adjourned sine die if the defendant is in prison and there is no prospect of continuing the action at that time. In a sine die adjournment of this type, the hearing stands open indefinitely, and could theoretically be resumed if the situation changed.
-- Wikipedia
Legal Definition
The act of suspending a trial or a hearing without fixing another date for the next session. It is a Latin phrase.