Ref: https://core.trac.wordpress.org/ticket/41620

The word "install" is a verb. The correct word to use when referring to an instance of WordPress is "installation".

There are several places in WP-CLI where "install" is used to refer to an installation.

• "This is not a multisite install" as an error message in several commands such as wp super-admin, wp core, the scaffold commands, and the entity commands.
• The success and error messages from wp core verify-checksums.
• wp find: A WordPress install is...
• wp core: Download, install, update and manage a WordPress install.
• wp super-admin: Lists, adds, or removes super admin users on a multisite install.
• Entity commands: Performs site-wide operations on a multisite install.
• Entity commands: Delete a site in a multisite install.
• Entity commands: Manage site options in a multisite install.
• The Given a WP install instruction in all Behat scenarios.

and most likely other places.

Non-code:

The GitHub repo description for:

• wp-cli/core-command
• wp-cli/find-command
• wp-cli/super-admin-command