Davis-Meyer is a method to construct a one-way compression function from a block cipher.
The Davis-Meyer construction is a way to construct a single-block one-way compression function from a block cipher. Using a one-way compression function built from a block cipher is a common way of designing hash functions hash.
The Davis-Meyer construction is $H' = E_{m}(H) \oplus H$ where $E$ is the block cipher's encryption permutation, $m$ is the message block input, $H$ is the hash state input and $H'$ is the new hash state.
