1. 基础训练；基础知识；基础
If you have a grounding in a subject, you know the basic facts or principles of that subject, especially as a result of a particular course of training or instruction.

1. fastening electrical equipment to earth

Synonym: earthing

2. education or instruction in the fundamentals of a field of knowledge

e.g. he lacks the foundation necessary for advanced study
a good grounding in mathematics

Synonym: foundation