What is Actual Notice?

Legal Definition
Actual notice is a law term, used most frequently in civil procedure. It is notice (usually to a defendant in a civil proceeding) delivered in such a way as to give legally sufficient assurance that actual knowledge of the matter has been conveyed to the recipient. Personal service, that is, physically handing something to an individual, is usually considered the least-disputable method of giving actual notice.

Actual notice may be contrasted with constructive notice, which is a way of giving notice that may not immediately bring the matter to the attention of the individual that is intended to receive the notice. Constructive notice includes, among other methods, service on an agent or family member, service by posting (on the front door), and service by publication (as in a newspaper).
-- Wikipedia
Legal Definition
Someone receiving notice (being informed of a case that could affect their interest - see: Notice) in fact, as opposed to Constructive Notice (where although that person did not receive notice in fact, the law will consider them to have received notice).

Note that constructive notice trumps actual notice. For example: Someone who is served improperly, but actually receives the papers may dismiss the case for lack of notice; while someone who is properly served (receives constructive notice), but because of a fluke does not in reality receive the papers will not be able to dismiss the case for lack of service.
Legal Definition
The notice handed to a party in person. They are presumed to have recieved it by their actions and knowledge.