1. over a large area or range; widely
2. to a great degree or amount; thoroughly

Examples

• The researcher traveled extensively throughout Europe to collect data.
• We discussed the proposal extensively before making a decision.
• The company has extensively tested the new product.
• Tropical rainforests are extensively used for timber and agriculture.
• She has studied extensively in the field of marine biology.
• The topic has been covered extensively in recent news reports.