As used in this part:

(a) Profit-sharing plan means any such program or arrangement as qualifies hereunder which provides for the distribution by the employer to his employees of their respective shares of profits;

(b) Profit-sharing trust means any such program or arrangement as qualifies under this part which provides for the irrevocable deposit by the employer of his employees' distributive shares of profits with a trustee for deferred distribution to such employees of their respective shares.