The noun grinder has 4 senses (no senses from tagged texts)
1. bomber, grinder, hero, hero sandwich, hoagie, hoagy, Cuban sandwich, Italian sandwich, poor boy, sub, submarine, submarine sandwich, torpedo, wedge, zep -- (a large sandwich made of a long crusty roll split lengthwise and filled with meats and cheese (and tomato and onion and lettuce and condiments); different names are used in different sections of the United States)
2. molar, grinder -- (grinding tooth with a broad crown; located behind the premolars)
3. mill, grinder, milling machinery -- (machinery that processes materials by grinding or crushing)
4. grinder -- (a machine tool that polishes metal)