-ful

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Full of: playful.
2. n. Characterized by; resembling: masterful.
3. n. Tending, given, or able to: useful.
4. n. A quantity that fills: armful.

Century Dictionary and Cyclopedia

1. n. A suffix attached to nouns to form adjectives denoting ‘full of …,’ ‘having…,’ as artful, awful, graceful, harmful, hopeful, peaceful, sinful, etc. It is also sometimes attached to verbs, as in bashful, bewitchful, etc., but in some such cases, as rueful, forgetful, etc., and in some other irregular instances, as grateful, a special explanation is to be sought in the history of the word.
2. n. A quasi-suffix attached to nouns denoting a containing thing, to form nouns expressing the amount or volume contained, as handful, armful, cupful, glassful, spoonful, bucketful, tubful, etc., meaning ‘as much as the hand, arm, spoon, etc., can contain or hold.’ In these compounds the second element has usually a fuller pronunciation than in the derivatives explained above.
3. A simplified spelling of full.

Wiktionary

1. n. Used to form adjectives from nouns. An adjective derived by this suffix implies a thorough and certain possession of the quality of that noun, not a metaphorical fullness with it by degree or quantity. One who is wakeful is fully awake, not frequently waking; what is changeful is uncertain, not transformed; what is harmful may do a single and a mild injury.
2. n. Used to form nouns from nouns meaning “as much as can be held by what is denoted by the noun”

GNU Webster's 1913

1. A suffix signifying full of, abounding with.

WordNet 3.0

1. n. a family of languages of the Fulani of West Africa and used as a lingua franca in the sub-Saharan regions from Senegal to Chad; the best known of the West African languages