neovim :imap but stay printing before to replace

I'm writing a mapping in neovim. Here is:

:imap abcd efgh

When I type 'abcd', it replaces by 'efgh'. This is the expected behavior.

But as typing 'abcd', it prints a, then replaces a by b, then replaces b by d and, finally when I type 'd', it prints efgh. My cursor never moves.

In other words I never see "abc" as a whole.

What I want is to see "abc" and then, when typing "d", the whole gets replaced by "efgh".

I kind of remember that, in vim-latexsuite, I had :call IMAP ("abcd", "efgh") which made the work.

Is it possible with nvim ?