Variable: isearch-word

Regexp-based search mode for words/symbols.
If t, do incremental search for a sequence of words, ignoring punctuation.
If the value is a function (e.g. `isearch-symbol-regexp'), it is called to
convert the search string to a regexp used by regexp search functions.
The property `isearch-message-prefix' put on this function specifies the
prefix string displayed in the search message.