Adjective

1. Of comparatively great physical weight or density
2. Unusually great in degree or quantity or number
3. Of the military or industry; using (or being) the heaviest and most powerful armaments or weapons or equipment
4. Marked by great psychological weight; weighted down especially with sadness or troubles or weariness
5. Of great intensity or power or force
6. (physics, chemistry) being or containing an isotope with greater than average atomic mass or weight