Dictionary file manager
Use the tools you have
The first thing I notice is that you're doing some work you don't need to. You're using a std::map to hold your keys and values, but you aren't utilizing the built-in method for finding an entry. (In other languages maps are actually named dictionary!) Your entire search_term() method could look like this:
bool dictionary::search_term(const std::string&amp; term){
    std::map&lt;std::string, std::string&gt;::iterator it = entries.find(term);
    return it != entries.end();
};

Likewise, the erase_entry() method could just call the std::map::erase() method.
Naming is hard
For the most part your variable and method names are pretty good! There are a few that I'd change, though. The exists() function should be something like file_exists() so it's not confused with checking if an entry exists in the dictionary.
Also, ofs_entries() and ifs_entries() are odd names. I'd call them something like write_entries_to_file() and read_entries_from_file().