LibreOffice is a full office productivity suite. It's a successor of the OpenOffice.org and strives to be a better and less bloated office suite.
emerge --ask --verbose app-office/libreoffice
Since LibreOffice is such a large package to compile, it is also offered in pre-compiled binaries in app-office/libreoffice-bin.
emerge --ask --verbose app-office/libreoffice-bin
The binary packages are compiled such that they fit to the libraries of a stable Gentoo system. You will encounter difficulties if you try to use them on an ~arch system; this is not supported.