for the purposes of section 17(1) means a lease which—
(a) was entered into for a period of not less than ten years;
(b) was entered into for the natural life of the lessee or of any other person mentioned in the lease; or
(c) is renewable from time to time at the will of the lessee indefinitely or for periods which, together with the first period, amount in all to not less than 10 years;
[Definition inserted by section 1(d) of Act 44 of 1997]