This message is generated when the level specifications in Outer are such that the elements that will be used as function arguments do not have the same tensor rank.
Off[message] switches off the message; On[message] switches it on. For example: Off[Compile::cpout].
Examples
Basic Examples(1)
Expressions with unequal tensor rank are used as arguments in Plus:
Wolfram Language code: Compile[{}, Outer[Plus, {1}, {{2}}, 1]]
This shows an expression that is compiled without error:
Wolfram Language code: Compile[{}, Outer[Plus, {{3}}, {{2}}, 1]]