Defined Benefit ...

Solving a bet with a fellow hr person ...

If you have a defined benefit pension, say 20 Years service done in semi state body ... do you loose this pension if you transfer to another job where there is a defined contribution pension only.

No, it would normally become a deferred pension benefit and will be paid from the normal retirement age as defined by the scheme. Of course, it will be based on the actual years of service in the job and not on the number of years actually worked.