(inorganic chemistry, in combination) Four arsenic atoms in a compound / (inorganic chemistry) The molecule that constitutes yellow arsenic. (As₄)

(informal) A period of time in the life of dogs, defined such that the average life expectancy of a dog in dog years is numerically equivalent to the average life expectancy of a human. A 4- and ...

present participle of zig-zag

plural of overoptimist