According to Merriam-Webster, brandishing is to shake or wave (something, such as a weapon) menacingly or exhibit in an ostentatious or aggressive manner.
Actions from resting your hand on the grip of your pistol or knife or sweeping your cover garment aside to expose your conceal carry weapon may be considered brandishing.
Most states do not have a legal definition of brandishing, but that doesn’t mean that brandishing a firearm, whether accidentally or with the intention of intimidating, won’t result in criminal charges.