a difficult problem

[ Syn: conundrum , enigma , brain-teaser ]

a coarse sieve (as for gravel)

pierce with many holes; The bullets riddled his body'

set a difficult problem or riddle; riddle me a riddle'

separate with a riddle, as grain from chaff

[ Syn: screen ]

spread or diffuse through; An atmosphere of distrust has permeated this administration; music penetrated the entire building; His campaign was riddled with accusations and personal attacks

[ Syn: permeate , pervade , penetrate , interpenetrate , diffuse , imbue ]

speak in riddles

explain a riddle