Tubārī is a third-person feminine singular imperfect of Form III, from b-r-y, meaning to keep pace with or compete. Its implicit subject hiya refers to the she-camel.
ʿItāqan denotes noble or well-bred animals and functions as the object; nājiyātin describes them as swift. As a sound feminine plural, nājiyāt can take kasrah in the accusative.
Connecting verb, subject, object, and adjective reveals a coherent action rather than a disconnected vocabulary list.