pentaquark: Word of the day for July 13, 2016

pentaquark , n :
(physics) Any of a class of subatomic particles (previously hypothetical, since detected, subject to confirmation) consisting of a group of five quarks (compared to three quarks in normal baryons and two in mesons), or more specifically four quarks and one antiquark (symbol Θ). The LHCb collaboration at CERN reported results consistent with pentaquark states in the decay of bottom Lambda baryons on this day in 2015.
July 13, 2016