a foreign visitor who is legally admitted to the United States for a specific authorized period and remains in the United States after that period expires, unless an extension or a change of status has been approved
an illegal alien who was legally admitted to the United States for a specific authorized period but remained here after that period expired, without obtaining an extension or a change of status or meeting other specific conditions
When visitors enter the United States on a visa, the Department of Homeland Security (DHS) U.S immigration USCISpector gives them a white card called an Arrival-Departure Record, Form or I-94. On this card the DHS, the U.S. immigration USCISpector records the length of time that visitors are permitted to stay in the United States. If the visitor stays longer than what the DHS permitted him/her to stay, he or she is considered an "overstay." The visitor may not be able to get another visa, depending on how long he/she "overstays" the visa.