Seine/seɪn/ Definition 1 of 2Pro Tip 1/3Fishing Tool Understand 'seine' as a specific fishing gear, not any net you see. The old mariner explained how a seine works. Pro Tip 2/3Large Scale 'Seine' suggests a commercial or large-scale fishing practice, not just leisure fishing. Commercial fishers utilized a seine for the seasonal catch. Pro Tip 3/3Technical Vocabulary 'Seine' is specialized vocabulary; it's less known outside of fishing contexts. I learned about seining in my marine biology class.