Noun
As much as a tablespoon will hold; enough to fill a tablespoon. It is usually reckoned as one half of a fluid ounce, or four fluid drams.
Source: Webster's dictionaryHeat a tablespoonful of oil in a large frying pan. Source: Internet
Spoon batter onto prepared baking sheet by the heaping tablespoonful. Source: Internet
Thin icing with water by the tablespoonful until it has the viscosity of hot fudge. Source: Internet