Rails 5 will introduce ActiveRecord::Relation#or. On Rails 4 and 3.2 you can use the activerecord_any_of Show archive.org snapshot gem which seems to be free of ugly hacks and nicely does what you need.

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Use it like this:

User.where.any_of(name: 'Alice', gender: 'female')

^
SELECT "users".* FROM "users" WHERE (("users"."name" = 'Alice' OR "users"."gender" = 'female'))

To group conditions, wrap them in hashes:

User.where.any_of({ name: 'Alice', gender: 'female' }, { name: 'Bob' }, { name: 'Charlie' })

^
SELECT "users".* FROM "users" WHERE ((("users"."name" = 'Alice' AND "users"."gender" = 'female' OR "users"."name" = 'Bob') OR "users"."name" = 'Charlie'))

It also brings none_of which will do the inverse.