pes·su·lus \-ləs\noun (pluralpessu·li \-ˌlī\) Etymology: Latin, bolt, modification of Greek passalos peg, stake; akin to Greek pēgnynai to fix, fasten together — more at pact : a bony or cartilaginous bar crossing the lower end of the windpipe of a bird dorsoventrally at its division into bronchi