sabbatical year

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

• noun A leave of absence from one's regular work responsibilities, usually with pay, for research, rest, or recreation. Many university professors are granted a sabbatical every seventh year.
• noun A year during which land remains fallow, observed every seven years by Jewish farmers in Israel.

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

• noun A year of rest for the land observed every seven years in ancient Judea, which included allowing the fields to lie without tilling, sowing, or reaping from one autumn to the next in accordance with a Levitical commandment.
• noun A leave, often with full or half pay granted (as every seventh year) to one holding an administrative or professional position for rest, travel, or research.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a sabbatical leave lasting one year