definition of
u

[1] #1 u n. [uracil, U] a base containing nitrogen that is found in RNA (but not in DNA) and derived from pyrimidine; pairs with adenine. wn

[2] #2 u s. (chiefly British) of or appropriate to the upper classes especially in language use. wn

[3] #3 u n. [uranium, U, atomic number 92] a heavy toxic silvery-white radioactive metallic element; occurs in many isotopes; used for nuclear fuels and nuclear weapons. wn

[4] #4 u n. [U] the 21st letter of the Roman alphabet. wn

[5] #5 u n. [U] the 21st letter of the Roman alphabet. wn