Commonly seen in the eligibility section of sweepstakes rules, "Contiguous United States" refers to the 48 states that do not include Alaska or Hawaii. "Contiguous" means "touching," and Alaska and Hawaii do not touch the other 48 United States.
If entry is open to the Contiguous US, that means that all residents of US states except for Alaska and Hawaii are eligible to enter.
Contiguous United States, Contiguous U.S.
To enter, you must be a resident of the contiguous United States and at least 18 years of age.