Teaspoonful
Teaspoonful (tē"spon`ful) , noun
In the 1890 dictionary, it was defined as a fluid dram or one quarter of a tablespoonful.
As much as teaspoon will hold; enough to fill a teaspoon. In cooking, it is usually estimated as 4.9 milliliters, which is ⅙ of a fluid ounce, or ⅓ of a tablespoonful. In cooking recipes it may be abbreviated as t.