1. extremely or very much, especially in a negative way
2. in a way that is obviously wrong or unacceptable

Examples

• The company was grossly negligent in handling customer data.
• She felt grossly underpaid for the amount of work she did.
• The movie was grossly overrated by critics.
• His behavior was grossly inappropriate for a professional setting.
• The estimate was grossly inaccurate.
• They grossly underestimated the time needed for the project.