handfast

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

• noun A handclasp used to signify a pledge, such as a contract or marriage.

from The Century Dictionary.

• To take or hold with the hand; hold securely or firmly; grasp.
• To join together by or as if by the clasping of hands; make fast; bind; specifically, to betroth.
• In some parts of Scotland, formerly, to marry provisionally by the ceremony of joining hands.
• Having a close hand; close-fisted.
• Bound by pledge, promise, or contract; especially, betrothed, or united as if by betrothal.
• In Scotland, formerly, joined in provisional wedlock.
• noun Grip; grasp; hold.
• noun Custody; power of confining or keeping; a holding on security or bail.
• noun A pledge, promise, or contract; especially, betrothal.

from the GNU version of the Collaborative International Dictionary of English.

• noun obsolete Hold; grasp.
• noun obsolete Custody; power of confining or keeping.
• noun obsolete A contract; specifically, an espousal.
• adjective obsolete Fast by contract; betrothed by joining hands.
• transitive verb obsolete To pledge; to bind.
• transitive verb obsolete To betroth by joining hands, in order to permit cohabitation, before the formal celebration of marriage; in some parts of Scotland it was in effect to marry provisionally, permitting cohabitation for a year, after which the marriage could be formalized or dissolved.
• adjective rare Strong; steadfast.

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

• adjective rare Strong; steadfast.
• noun obsolete A hold, grasp; custody, power of confining or keeping.
• noun obsolete A contract, agreement, covenant ; specifically betrothal, espousal.
• verb transitive To pledge; to bind
• verb transitive, Wicca To betroth by joining hands, in order to allow cohabitation before the celebration of marriage; to marry provisionally.
• adjective obsolete Fast by contract; betrothed by joining hands.