[1] : The Collaborative International Dictionary of English v.0.48

useful \use"ful\, a.
   full of use, advantage, or profit; producing, or having power
   to produce, good; serviceable for any end or object; helpful
   toward advancing any purpose; beneficial; profitable;
   advantageous; as, vessels and instruments useful in a family;
   books useful for improvement; useful knowledge; useful arts.
   1913 webster

         to what can i useful                    --milton.
   1913 webster

[2] : WordNet (r) 2.0

useful
     adj 1: being of use or service; "the girl felt motherly and
            useful"; "a useful job"; "a useful member of society"
            syn: utile ant: useless
     2: of great importance or use or service; "useful information";
        "valuable advice" syn: valuable, of value
     3: capable of being turned to use or account; "useful
        applications of calculus"
     4: having a useful function; "utilitarian steel tables" syn: utilitarian
see also:
utile useless valuable of value utilitarian 

[3] : Moby Thesaurus II by Grady Ward, 1.0

117 moby thesaurus words for "useful":
   advantageous, advisable, agential, agentival, agentive, aidful,
   appropriate, assisting, auspicious, banausic, becoming, befitting,
   beneficial, benevolent, bon, bonny, brave, braw, bueno, capital,
   cogent, commendable, commodious, conducive, congruous,
   constructive, contributory, convenient, decent, desirable,
   effective, elegant, employable, estimable, excellent, expedient,
   facilitating, fair, famous, favorable, favoring, feasible,
   felicitous, fine, fit, fitten, fitting, forwarding, fructuous,
   fruitful, functional, furthersome, gainful, good, good for, goodly,
   grand, handy, happy, healthy, helpful, instrumental, intermediary,
   kind, laudable, likely, mediating, mediatorial, meet, ministerial,
   ministering, nice, noble, of general utility, of help, of service,
   of use, opportune, pleasant, politic, positive, practicable,
   practical, pragmatical, productive, profitable, promoting, proper,
   propitious, recommendable, regal, remedial, right, royal, salutary,
   seasonable, seemly, serviceable, skillful, sortable, sound,
   splendid, subservient, suitable, therapeutic, timely,
   to be desired, toward, usable, utilitarian, valid, valuable,
   very good, virtuous, well-timed, wise, worthwhile

[4] : Bouvier's Law Dictionary, Revised 6th Ed (1856)

useful. that which may be put into beneficial practice. 
     2. the patent act of congress of july 4, 1836, sect. 6, in describing 
the subjects of patents, mentions "new and useful art," and "new and useful 
improvement." to entitle the inventor to a patent, his invention must, to a 
certain extent, be beneficial to the community, and not be for an unlawful 
object, or frivolous, or insignificant. 1 mason, 182; 1 pet. c. c. r. 322; 1 
bald. 303; 14 pick. 217; paine, 203. 

Useful >> U Words
Useful, definition of term: Useful
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