Definition
Regular scheme
A locally Noetherian scheme whose local rings are regular.
A scheme is regular if it is locally Noetherian and each local ring is a regular local ring. Here locally Noetherian means that every point has an affine open neighborhood with Noetherian coordinate ring.
Interpretation
The local rings are the stalks of the structure sheaf of the underlying locally ringed space. Thus this definition concerns the scheme itself and does not require a chosen base field.