Definition of pinch out:
(v) :
To remove the shoots of a plant:
(v) :
the leading shoot in order to encourage a bushy habit
(v) :
a plant's side shoots
(n) :
(mining, geology) A volume of rock or oil trapped or isolated between strata that have pinched it out.
(v) :
(mining, geology) For a distinct body of rock between underlying and overlying strata, to thin out and come to an end, so that the strata above come to lie on the strata below.