To keep in existence; maintain. To supply with necessities or nourishment; provide for. To support from below; keep from falling or sinking; prop. To support the spirits, vitality, or resolution of; encourage. To bear up under; withstand: can't sustain the blistering heat. To experience or suffer: sustained a fatal injury. To affirm the validity of: The judge has sustained the prosecutor's objection. To prove or corroborate; confirm. To keep up (a joke or assumed role, for example) competently.