Tattarrattat, defined as a knock at the door, is the longest English language palindrome and also an onomatopoeia.
And now for the coordinates
meow
crunch
smash
screech
thump
whoosh
kayak
whizz
chortle
buzz
rotator
cock-a-doodle-doo
hiss
civic
racecar
purr
ribbit
warble
bloop
squirt
level
eek
mom
radar
tweet
deified
honk
ding
clank
thud
bang
repaper
madam
giggle
squeal
noon
You can validate your puzzle solution with certitude.
This has nothing to do with the puzzle but I thought you'd like to know that tattarrattat was first used by James Joyce in 'Ulysses'.