ABJECT (נָכָה, H5782, smitten ones). A word used to describe some low outcasts who gathered together against the psalmist (Ps 35:15 KJV, ASV; RSV “cripples”). The word rendered “abjects” is of doubtful meaning and may be corrupt.

International Standard Bible Encyclopedia (1915)

ab’-jekt: Only as a noun, and but once (Ps 35:15) for nekheh, literally, "smitten ones," i.e. "men of the lowest grade" (Hengstenberg, Delitzsch), "the rabble," defined by the succeeding clause as those of such inferior station that they were unknown.