The present study investigated the effects of 2 forms of text-based second language (L2) vocabulary glosses, namely dynamic and nondynamic glosses on EFL learners' vocabulary knowledge. Dynamic glosses were operationalized as a set of incrementally ordered mediating annotations designed to help learners identify the correct word definition while nondynamic glosses were operationalized as traditional fixed word definitions. During 2 treatment sessions, the participants in the 2 experimental groups as well as the control condition were presented with several short passages that included a number of unknown words via the Telegram application using learners' smartphones. The participants in the dynamic glossing condition were presented with a set of graduated prompts ordered from the most implicit to the most explicit for each unfamiliar word to identify its correct definition while reading the short passages. For the mobile-mediated nondynamic glossing condition, the learners were directly provided with a first language (L1) definition for each target word while reading the same text via their smartphones. The results of posttests and delayed posttests provided evidence for the benefits of the 2 mobile-mediated glossing conditions and also the superiority of the dynamic glossing condition over nondynamic glossing condition for L2 vocabulary learning.