The term 'SIBILANT SUMMONS' is a combination of two words, 'SIBILANT' and 'SUMMONS'. SIBILANT is an adjective that describes a sound made by air passing through a narrow opening, such as a hiss or a whistle. A SUMMONS is an authoritative call or demand, usually from a court or other authority. Together, the two words create a phrase that implies a loud, authoritative call for attention. The crossword solutions for this term are 'psst' (4 letters) and 'pssst' (5 letters). Both of these words are onomatopoeic, meaning they imitate the sound they represent. Psst is a whispered sound used to get someone's attention, while pssst is a slightly louder version of the same sound.