Well take a look at some of the amendments that they have been lodging in the House of Lords.
Looks like a redefinition to me, of course this only applies to those of same-sex couples as can be seen by a withdrawn amendment on the same line:
LORD CORMACKPage 1, line 5, leave out “Marriage” and insert “Union”
LORD MACKAY OF CLASHFERNPage 1, line 5, at end insert “and shall be referred to as “marriage (same sex
But apparently marriage as we know it now is no longer good enough for those that are married. It needs redefined and renamed....
Read the full list of redefinitions and comments about them on LGBT+ Lib Dems Northern Ireland