Alias in bash to Change Directory
You need to escape/protect any spaces etc in the path:

alias cdicloud="cd ~/Library/Mobile\ Documents/com~apple~CloudDocs"


Executing this in Terminal looks like the following:

pse@Mithos:~$ alias cdicloud="cd ~/Library/Mobile\ Documents/com~apple~CloudDocs"
pse@Mithos:~$ cdicloud 
pse@Mithos:~/Library/Mobile Documents/com~apple~CloudDocs$ cd -
/Users/pse
pse@Mithos:~$