Display screen or portion thereof with transitional graphical user interface

FIG. 1 is a front view of a display screen or portion thereof with transitional graphical user interface showing a first image in a sequence;

FIG. 2 is a second image thereof; and,

FIG. 2A is an enlarged view of the region indicated by the dot-dash line indicia and legend in FIG. 2 .

The subject matter in this patent includes a process or period during which an image sequentially transitions between the images shown in FIGS. 1-2 . This process or period forms no part of the claimed design.

The thick broken lines shown in FIG. 2 are included as a feature of the claimed design.

The thin broken lines illustrate a portion of display screen of a communications terminal, text, and icons and form no part of the claimed design.

The dot-dash lines in FIG. 2 indicate the perimeter of a portion shown enlarged for clarity in FIG. 2A and form no part of the claimed design.