A waste of breath the years behind is what meter

The line "A waste of breath the years behind" is in iambic tetrameter.

One meter consists of two syllables. So if we look at the line, we see there are 8 syllables: "A/waste/of/breath/the/years/be/hind." This means there are four meters. In a poem, this is called tetrameter.

A poem is called iambic when the syllables follow a pattern of stressed and unstressed syllables. The pattern is stressed, unstressed, stressed, unstressed, etc ...