What is Quaerens Non Invenit Plegium?

Legal Definition
Practice. The plaintiff has not found pledge. The return made by the sheriff to a writ directed to him with this clause, namely, si A facerit B securum de clamore suo prosequando, when the plaintiff has neglected to find sufficient security. F. N. B. 38.
-- Bouviers Law Dictionary
Legal Definition
The plaintiff has not found security.
-- Ballentine's Law Dictionary