Exotic atom
A hadronic atom is an exotic atom that has an electron replaced by a negatively charged hadron. The hadron could be a meson (such as a pion or a kaon, creating a pionic atom or a kaonic atom, respectively). Another hadronic atom is an antiproton (antiparticle of the proton) atom, that has an antiproton replacing an electron. This is known as an antiprotonic atom.