In optics, descriptive of a material that allows light to pass through it relatively unimpeded, or possesses a high degree of transparency. The opposite is an opaque substance.
In computers, transparent is descriptive of any function or operation performed by the computer automatically while the user is performing another, perhaps unrelated function. A transparent function is not apparent to the operator (or even to other devices). Transparent software is a computer program that can be added to an original program and function seamlessly with that program without the operator having to re-learn the program.