neutral zone

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Football An imaginary area as wide as the length of the football extending across the field between the lines of scrimmage, in which the presence of any player other than the center at the snap of the ball constitutes a violation of the rules.
• noun Sports The area of an ice hockey rink between the two bluelines that is neither an offensive nor a defensive zone.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun American football zone between the defensive line of scrimmage and the offensive line of scrimmage.
• noun ice hockey zone on the playing surface between the attacking zone and the defending zone as delineated by the two blue lines.