Hi at all
in this sentence
to move slowly or with difficulty, especially (of a person) with the body stretched out along the ground or on hands and knees.
In my dictionary i don't find the word stretched.
I want to know if it is an adjective.
In this context it is an adjective You'll find it at OneLook Dictionary Search. Take a look at this link; you'll find the definition under the heading Adjectives. WordNet 3.0 Vocabulary Helper: stretched