This poem is divided into nine eight-line stanzas, or octaves ("octa" means "eight"…and yep, an octopus has eight legs), each with a regular ABABCDCD rhyme pattern. Below is an example of what we mean. We'll assign a letter for each end-rhyme:
Gr-r-r--there go, my heart's abhorrence! (A)
Water your damned flower-pots, do! (B)
If hate killed men, Brother Lawrence, (A)
God's blood, would not mine kill you! (B)
What? your myrtle-bush wants trimming? (C)
Oh, that rose has prior claims— (D)
Needs its leaden vase filled brimming? (C)
Hell dry you up with its flames! (D)
The rhyme scheme and number of lines per stanza are very regular and predictable, but the meter – the pattern of stressed and unstressed syllables per line – is irregular.
We define the meter of this poem as trochaic tetrameter because most of the lines have four stressed syllables ("tetra" means four… like how Tetris shapes are all made of four blocks). "Trochaic" describes the pattern of those stressed syllables. A trochee is a stressed syllable followed by an unstressed syllable (DA-dum). Take a look at line 5. If we bold the syllables that you would naturally stress as you say the words, it would look like this:
What? your myr-tle bush wants trim-ming?
So the pattern is DA-dum, DA-dum, DA-dum, DA-dum. Four trochees. Trochaic tetrameter.
Of course, the speaker gets carried away a lot, so often this meter gets thrown out the window. Still, the regularity of the stanzas and the rhyme scheme keep the poem from getting too chaotic. Later dramatic monologues by Robert Browning don't have a regular rhyme scheme at all. What's the effect of the regularity in this poem? Why would Browning keep some aspects of the form, like the rhyme scheme, regular, while allowing the meter to be so irregular?