Not quite up to full measure For example: a scant teaspoon of an ingredient would be less than a teaspoonful as opposed to a level teaspoon, rounded teaspoon or heaping teaspoon
Not full, large, or plentiful; scarcely sufficient; less than is wanted for the purpose; scanty; meager; not enough; as, a scant allowance of provisions or water; a scant pattern of cloth for a garment
You use scant to indicate that there is very little of something or not as much of something as there should be. She began to berate the police for paying scant attention to the theft from her car