Alternative spelling of R & B

(physics, astronomy) The relatively rapid nucleosynthesis process, in supernovae, in which a large neutron flux allows rapid neutron capture and synthesis of elements up to the transuranic elements.

(organic chemistry) A crystalline sulfonic acid, HOC₁₀H₅(SO₃H)₂, derived from beta naphthol and used as a dye intermediate; 2-naphthol-3,6-disulfonic acid.

(algebra) The monoid action of a ring R on an abelian group.

plural of r-word

(euphemistic) The word rape, regarded as a vulgar or taboo word. / (euphemistic) The word retard, regarded as a vulgar or taboo word.

(medicine) Initialism of rule out: used to indicate that a certain possible diagnosis should be considered, and appropriate tests performed to rule it out.

(phonology) The omission of the sound of a letter "r" after a vowel.

(informal) Robert Pattinson (born 1986), English actor

plural of r-value