The definition and concept of technology has changed numerous times as humanity passed through the different ages and levels of intellectual understanding. Until fairly recently "technology" would have conjured images of machinery and tools, intended to make work and life both easier and more productive. Luckily, this has frequently applied to learning as well, with each new advancement providing new opportunities for both the educator and the learner.
However, a more encompassing view of it as a tool is required for 21st century technology and learning. There are multiple definitions and metaphors available, but I find I have the most in common with this one from Totter (1998) and Kozma (2003):
"[T]echnology is not a vitamin whose mere presence in schools catalyzes better educational outcomes; nor are new media just another subject in the curriculum, suited primarily for teaching technical literacy….Instead, emerging interactive media are tools in service of richer curricula, enhanced pedagogies, more effective organization structures, stronger links between schools and society, and the empowerment of disenfranchised learners."
As I favour a practical use and disposition towards ideas and theories, this definition appeals since it identifies what technology is not and then on the flip-side offers up what it can be for the educator and the learner. Thus one can generate tangible ideas from the definition even though it is quite broad. The view that it is still a tool also resonates well, since the effectiveness of a tool is not absolute, but rather is dependent upon how it is applied, and new users may find novel uses for a tool. However, I would opt to make two modification to this definition. The first would be to remove "disenfranchised" and the second would be to add "self-discovery" so that the end of the definition reads, "…and the empowerment and self-discovery of learners."
References
Kozma, R. (2003). Technology, innovation, and educational change: A global perspective, (A report of the Second Information Technology in Education Study, Module 2). Eugene, OR: International Association for the Evaluation of Educational Achievement, ISTE Publications.
Trotter, A. (Ed.) (1998). Technology counts 1998: Putting school technology to the test (special report). Education Week, 18(5).