Two words. Although it technically only refers to receivers set out “wide” from the formation, in everyday speech it can be used to refer even to receivers to usually set up in the slot.

For a general audience, if positional specificity is required, informal terms such as primary receiver or secondary target are preferable over fantasy football designations such as “WR1,” which should only be used in gaming contexts; for a more technical audience, terms such as X receiver, Y receiver, Z receiver, etc. are more appropriate.

See: football positions