Note: this error code is no longer emitted by the compiler.

An undefined atomic operation function was declared.

Erroneous code example:

#![feature(intrinsics)]
#![allow(internal_features)]

#[rustc_intrinsic]
unsafe fn atomic_foo(); // error: unrecognized atomic operation
                        //        function

Please check you didn‘t make a mistake in the function’s name. All intrinsic functions are defined in library/core/src/intrinsics in the Rust source code.