Synonyms:

yada–when; samharate–winds up; ca–also; ayam–all these; kurmah–tortoise; angani–limbs; iva–like; sarvasah–altogether; indriyani–senses; indriya-arthebhyah–from the sense objects; tasya–his; prajna–consciousness; pratisthita–fixed up.

Trasnslation:

One who is able to withdraw his senses from sense objects, as the tortoise draws its limbs within the shell, is to be understood as truly situated in knowledge.