I used to use CShell (csh), which lets you make an alias that takes a parameter. The notation was something like
alias junk=\"mv \\\\!* ~/.Trash\"
As has already been pointed out by others, using a function should be considered best practice.
However, here is another approach, leveraging xargs:
xargs
alias junk="xargs -I "{}" -- mv "{}" "~/.Trash" <<< "
Note that this has side effects regarding redirection of streams.