  A coherent perfect absorber is capable of completely absorbing input waves.
However, the coherent perfect absorption severely depends on the superposition
of the input waves, and the perfect absorption is sensitive to the disorder of
the absorber. Thus, a robust incoherent perfect absorption, being insensitive
to the superposition of input waves and the system disorder, is desirable for
practical applications. Here, we demonstrate that the linearly independent
destructive interference at the port connections removes the constraint on the
coherent input. We propose an approach using the interplay between the loss and
localization to form the incoherent perfect absorption. The resonant incidence
from either port is completely absorbed. Furthermore, we utilize the lattice
configuration supporting the flat band to demonstrate the disorder-immune
incoherent perfect absorption. Our findings provide insight into the
fundamentals and applications for the perfect absorption of light, microwaves,
sound, mechanical waves, and beyond.
