This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

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adj. Acting directly to produce an effect: an efficient cause. See Synonyms at effective.

adj. Acting or producing effectively with a minimum of waste, expense, or unnecessary effort.

adj. Exhibiting a high ratio of output to input.

adj. Making good, thorough, or careful use of resources; not consuming extra. Especially, making good use of time or energy.

adj. Using a particular proportion of available energy.

adj. Causing effects; producing results; that makes the effect to be what it is; actively operative; not inactive, slack, or incapable; characterized by energetic and useful activity.

n. An efficient cause; a prime mover.

Producing outward effects; of a nature to produce a result; active; causative.

Acting or able to act with due effect; adequate in performance; bringing to bear the requisite knowledge, skill, and industry; capable; competent: as, an efficient workman, director, or commander.

Synonyms Efficacious, Effectual, etc. (see effective); energetic, operative, active, ready, helpful.

n. An efficient cause (see above).

n. One who is efficient or qualified; specifically, in the volunteer service of Great Britain, one who has attended the requisite number of drills, and in respect of whom the corps receives the capitation grant paid by government.

n. In mathematics, a quantity multiplied by another quantity to produce the quantity of which it is said to be an efficient; a factor.

adj. able to accomplish a purpose; functioning effectively

adj. being effective without wasting time or effort or expense

"If he left the "road" and became a _very_ efficient common laborer, some _ordinarily efficient_ common laborer would have to take to the "road.""

competent    streamlined    economical    businesslike    cost-effective    economic    expeditious    high-octane    cost-efficient   

inefficient   

extra efficient    efficient cause   

effectual    efficacious    effectivity    efficacity    subefficiency    effectuate    efficacy    effective    subefficient    effect   

effectual    potent    competent    able    capable    material    effective   

Omniscient    beneficent    coefficient    deficient    inefficient    insufficient    omniscient    proficient    self-sufficient    sufficient   

effective    powerful    reliable    direct    energetic