Running or performing extremely smoothly, especially (music, slang) playing perfectly, perfectly in sync with others, or with perfect focus.
Used other than figuratively or idiomatically: see in, groove.
Coherent; well organized.
Into one place; into a single thing; combined.
It has been raining four days together
Without intermission or interruption; continuously; uninterruptedly.
At the same time, in the same place; in close association or proximity.
In a relationship or partnership, for example a business relationship or a romantic partnership.