weighten

verb4

1. •
   To add or give weight to; make heavy

   • The idea of all this shifting was simply to weighten the bows, thereby lightening the stern, and so obtain the utmost hydrodynamic benefit. — 2001
2. •
   To weigh down

   • Efforts were made to cheer the King, and rouse him from the depression with which his sorrows began to weighten him. — 1880
3. •
   To become heavy

   • Her lids weightened, slightly hooding violet eyes that mesmerically followed the teardrop trailings. — 1987
4. •
   (figurative) To give support or importance to; make weighty