Teaspoonful n. : As much as teaspoon will hold; enough to fill a teaspoon; -- usually reckoned at a fluid dram or one quarter of a tablespoonful.

Example:
How many CC is a half of Teaspoonful?

Taxonomy
teaspoon, one teaspoon, spoon, mL, tablespoon, ingredients, free encyclopedia, Measure, teaspoonful, liquid, measuring spoons, American English, Cooking weights and measures, coffee spoon, bar spoon, Articles lacking sources, cutlery, a cup of tea.

Defination from the web:
teaspoonful — as much as one teaspoon can hold — is used as a unit of volume, especially in cooking recipes and pharmaceutic ... If a recipe calls for a teaspoonful of a powder ingredient (salt, flour, etc.), this normally refers to an approximately levelled ...