The meter of the poem is iambic tetrameter. "Iambic" refers to the weak/strong pattern of rhythm in the syllables in the lines. "Tetrameter" refers to the number of rhythm units (feet) in the lines; in this poem there are four feet per line.
Here are two lines from the poem with the meter marked. The bold words or syllables are the accented or strong beats; the feet in each line are divided by the / mark:
I have / a ren /dezvous / with Death
At some / dispu /ted bar /ricade
The weak/strong pattern here is iambic, and there are four iambs (units of rhythm) in each line: iambic tetrameter.