Definition: (1) fully accomplished in an art, science, or career; (2) having great knowledge and experience in a trade or profession

Derivation: Latin, “to go forward”

Synonyms: Proficient implies a thorough competence derived from training and practice; adept implies special aptitude as well as proficiency; expert implies extraordinary proficiency and often connotes knowledge as well as technical skill; skilled stresses mastery of technique; skillful implies individual dexterity in execution or performance.

• The hard thing about all these tools is that it takes a fair amount of effort to become proficient.  Bill Nelson Joy (1954-) American computer engineer
• We need visions of a future in which we have applied our infinite creativity to the task of living on a finite world, where we have embraced our role, become comfortable and proficient as planet-shapers, and learned to use our technological skills to enhance the survival prospects not just of humanity but of all life on Earth. — David H. Grinspoon (1959-) American astrobiologist