There are many synonyms that can be used in place of the phrase "well-grounded thorough." Some examples include "comprehensive," "in-depth," "detailed," "rigorous," "meticulous," "systematic," "methodical," "complete," and "thoroughgoing." These words all convey a sense of deep knowledge and expertise on a subject. A person who is well-grounded thorough is someone who has a deep understanding of a topic, has investigated it thoroughly, and can provide detailed and accurate information. Whether you are writing a paper, giving a presentation, or simply sharing information with others, using synonyms for "well-grounded thorough" can enhance your communication and help you convey your knowledge and expertise to others.