Brown-Driver-Briggs
[
רִקּוּעַ]
noun [masculine] expansion; — plural construct
וְעָשׂוּ אֹתָם רִקֻּעֵי פַחִים Numbers 17:3 expansions of plates, i.e. they shall be beaten into
broad plates. I. רקק (√of following; Arabic 
be thin, also figurative be weak, slender, scanty, etc.; Ethiopic 
be thin, 
thin; Syriac 
Pa`el, Aph`el make thin, 
thin).
