Verbal. adj. 3. spoken rather than written (a ------ contract).
Merriam Webster Collegiate Dictionary, 10th ed.

Verbal. 4. "Expressed or conveyed by speech rather than writing; stated or delivered by word of mouth; oral."
Example- 1728, Chambers Cyclopaedia- "A verbal contract is that made merely by word of mouth; in opposition to that made in Writing."
Oxford English Dictionary.

In court of law, it is a 'verbal contract.'