noun

• (vehicles, agriculture) A small spacer located on top of the axle of horse-drawn wagons that gives the front wheels enough clearance to turn.
• (architecture) The rolls forming the ends or sides of the Ionic capital.
  "Its [the Ionic's column's] ancient capital is generally formed of two parallel bolsters"
• (military, historical) A block of wood on the carriage of a siege gun, upon which the breech of the gun rests when arranged for transportation.
• (figurative) That which supports or promotes; a catalyst.
  "My health too has been better since you took away that Montero cap. I have left off cayenned eggs and such bolsters to discomfort."

verb

• (transitive, often figurative) To brace, reinforce, secure, or support.
  "Puget also teamed up with Matt Hyde (Deftones, Slayer) to co-produce the record, which was another smart move: Together, the pair ensures that AFI (The Blood Album)'s arrangements are streamlined, but bolstered by just the right amount of atmospheric texture."