This study took place in the online 3D virtual world Second Life[R], a recreational environment designed for world-building and socializing, and intended for individuals 18 years old and older. It described learning from the perspective of Second Life[R] Residents and focused on their world-building activities. As a virtual ethnographer, my avatar interacted with seven main participant-avatars in-world. Real life ages ranged from 33 years old to mid 50s; all but one were women. I collected data from 20 other Residents also. The study contributes to a nascent body of educational research exploring new forms of inquiry and practice conceived in virtual worlds, and breaks new ground by positioning itself in terms of a constructionist-learning context in which adults actively engage. The findings reiterate previous research of learning in virtual worlds. It is situated, social, intrinsically engaging and requires a high degree of personal agency. Learning in Second Life [R], however, typifies constructionist principles, and qualities of adult learning which, in practice, are relevant to children as learners too. The context-specific activities of world-building invoke in learners a capacity to be self-directed problem-solvers of concrete and personally meaningful tasks. These activities result in novel expressive forms, and performative expressions of self through one's avatar. World-building engenders artists' and artisans' habits of mind in the forms of learning-by-doing and trial and error. Compared with the larger population, Second Life[R] Residents are trailblazers. I therefore proposed cyborg learners/learning as a formulation for characterizing the expressive forms and ways of learning documented here. (1) Learners embody avatars in a 3D graphical space. (2) They are geographically dispersed. (3) They occupy at least two or more social and technological locations simultaneously. (4) Learning is technologically and socially platform-specific. (5) It is socially interdependent. (6) It depends on intrinsically motivating activities. (7) It engenders forms of learning-by-doing. These findings contribute to a broad research paradigm addressing games for learning, mobile learning, open learning, personal learning environments (PLEs) and multi-user learning environments (MUVEs). [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]