noun

a long, thick pillow that is placed under other pillows for support.

pillow,cushion,pad,support,rest

verb

support or strengthen.

the fall in interest rates is starting to bolster confidence

strengthen,support,reinforce,make stronger,boost,fortify,give a boost to,prop up,buoy up,shore up,hold up,maintain,buttress,brace,stiffen,uphold,aid,assist,help,supplement,augment,feed,add to,increase,revitalize,invigorate,renew,regenerate