I can't find a dictionary widget anywhere

Apple includes a dictionary application in your Applications folder. In its Preferences, you select, and drag the dictionaries in the order you want them to appear on the Dictionary application's toolbar. Once done, drag and drop the Dictionary application dead center of your Dock, where it is a single click away. Here is my interface:

You also have alternatives to use this dictionary for word lookups:

1. control+command+D with your pointer hovering over an (unselected) word that you want to look up.
2. When configured in trackpad preferences, three-finger tap to also invoke a lookup when hovering over a word
3. You can launch the Dictionary application with the result of a word entered in a Safari URI:
   1. dict://mystery
   2. Safari will prompt you for permission to open the dictionary application with that word.

Also in most macOS & OS X, with advent of Launchpad in the Dock

you could open and have access to most things, with a single-click.

Plus an old school access-point may be created with an Alias, too.

Good luck & happy trails!🍀🐎