What are the differences in pronunciation of "borrow", "burrow" and "burro" in American English?

What are the differences in pronunciation of "borrow", "burrow" and "burro" in American English? To me they all sound quite the same, especially when spoken quickly.

• QUESTION: What dictionaries did you first consult looking for an answer to this, and what did they say that so confused you? This really is nothing more than a “look it up in a dictionary” question from what I can see.

I believe that in most North American speakers:

• borrow is either of [ˈbɑɹoʊ] or [ˈbɔɹoʊ]. The first is perhaps the more common of the two, but both occur and are unremarkable. For comparison purposes, the first has the vowel of bar [bɑɹ], while the second has the vowel of war [wɔɹ]. Depending on how that particular speaker’s take on the cot–caught merger falls out, it may also be [ˈbɒɹoʊ], which is somewhere between the two extremes.
• burrow is [ˈbʌɹoʊ] (well, or [ˈbɜɹoʊ], if those are different to you). It has the same vowel as bird or hurry.
• burro is usually [ˈbʌɹoʊ] but in the American Southwest especially is sometimes [ˈbuːɹoʊ] due to its Spanish pronunciation of [ˈburo].
• borough is either of [ˈbʌɹoʊ] or [ˈbʌɹə]. The last of those sounds like the place where the cackling kooks hang out: the Kookaburra. :) I can see someone not familiar with the word saying [ˈbɔɹoʊ] for it, thought that doesn’t sound right to me.

In other words, the words borrow, burrow, burro, and borrow are commonly pronounced as any of [ˈbɑɹoʊ], [ˈbɒɹoʊ], [ˈbɔɹoʊ], [ˈbʌɹoʊ] / [ˈbɜɹoʊ], [ˈbuːɹoʊ], or [ˈbʌɹə], but precisely which pronunciation goes with which word varies considerably by speaker.

I don’t know that any speaker ever makes all four of those homophones with just one single pronunciation covering all of them, but certainly several possible pairs from that list can be exact homophones in certain speakers and yet in other speakers not homophones at all.

This may be what you are hearing, or think you’re hearing. I say “think” because some of those can be close enough in rapid speech as to be hard to tell apart without contextual clues.

PS:

The somewhat similarly written barrow is never homophonous with any of the set listed above, but just which vowel it has again depends on the speaker. Any of [ˈbeɹoʊ], [ˈbɛɹoʊ], or [ˈbæɹoʊ] is possible, with the first of those perhaps the most common and the last surely the least. Expect barrow to sound like the start of barrel and to rhyme with arrow, sparrow, and narrow in the same speaker, however that ends up.

Here is an extensive list of words following a similar pattern to those you first asked about:

barrow, borough, borrow, buroo, burro, burrow, burru, cero, charro, churro, claro, douro, faro, farrow, furrow, guru, gyro, harrow, hero, hurroo, karo, kero, koru, kuru, marrow, merow, merrow, miro, morro, morrow, muru, narrow, pleuro, pyro, ruru, sbirro, serow, sorrow, sparrow, taro, tarrow, thorough, tiro, toro, tyro, wharrow, yarrow, zero

That is, they follow the pattern CVRO, which C is one or consonants, V is one more vowels, R is one or more r’s, O is one or more o’s or u’s, and silent bits don’t count.

If prefixes and combining forms count, you can add these to your list:

boro‑, cero‑, chiro‑, chloro‑, cirro‑, clero‑, ferro‑, fluoro‑, furrow‑, gyro‑, hiero‑, mero‑, neuro‑, phloro‑, pleuro‑, ptero‑, puro‑, pyro‑, sauro‑, scirrho‑, sclero‑, sero‑, sphaero‑, sphero‑, spiro‑, sporo‑, stauro‑, stearo‑, tauro‑, thero‑, thoro‑, thorough‑, thyro‑, thyro‑, viro‑, xero‑

I don't know the international phonetic symbols, but I'll try to help anyway.

The first word, "Borrow" is pronounced more like "BAR O" where "Burrow" and "Burro" are pronounced the same, "BUR O". If the speaker has any Spanish influence, you might hear a slight difference as they might pronounce "Burro" a little differently, perhaps trilling the "rr" and/or changing the vowel like "BORE O".