Generally used in programming terms. Means to add something to a string or variable.
Append " dictionary" to "urban".

PHP Example:
$var = "Urban";
/* append to var */
$var .= " Dictionary";
by suspended chaos September 19, 2004
An agonising, unwelcome, erect, inflamed penis causing havoc inside your body.
Though normally flaccid, Tom's appendix throbbed vigorously causing appendicitis.
by Spongebob Shit Pants May 12, 2020