Fundamental of a bash builtin command named “unalias”

ABOUT unalias

Remove each name from the list of defined aliases.  If -a is supplied, all alias definitions
are removed.  The return  value  is true unless a supplied name is not a defined alias.

[bash]
$unalias
unalias: usage: unalias [-a] name [name …]
$echo $?
2
$unalias -a
$echo $?
0
$unalias pwd
bash: unalias: pwd: not found
$pwd
/home/jeffrin
$alias ls list
bash: alias: ls: not found
bash: alias: list: not found
$alias list ls
bash: alias: list: not found
bash: alias: ls: not found
$alias pwd pwf
bash: alias: pwd: not found
bash: alias: pwf: not found
$alias
$alias list="ls"
$unalias list
$echo $?
0
$list
bash: list: command not found
$

[/bash]

LINK
https://www.quora.com/What-is-the-alias-unalias-command-in-Unix