The process of removing bulk without shortening hair length is:

Texturizing is a technique used in haircutting to remove bulk from the hair while maintaining its overall length. This process can involve the use of various tools, such as scissors or razors, to create layers and enhance the texture of the hair without significantly altering its length. By selectively removing some of the hair strands, texturizing adds movement and volume, making the hair easier to style and manage.

Beveling, tapering, and stacking all primarily focus on shaping and altering the length of hair in specific ways, which can involve shortening or creating defined edges. In contrast, texturizing is specifically aimed at refining the hair's volume and texture without the intention of making it shorter, which distinguishes it from the other techniques listed in the question.