Display Screen or Portion Thereof with Transitional Icon

FIG. 1 is the first image in a sequence for a display screen or portion thereof with transitional icon showing my new design;

FIG. 2 is the second image thereof;

FIG. 3 is the third image thereof;

FIG. 4 is the fourth image thereof; and,

FIG. 5 is the fifth image thereof.

The outer perimeter illustrated by a pair of dashed broken lines in the drawings illustrates a display screen or portion thereof and forms no part of the claimed design. The dot-dash broken lines in the drawings define the boundaries of the claimed design and form no part thereof.

The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1 - 5 . The process or period in which one image transitions to another images forms no part of the claimed design.