Definition - What does Aerate mean?
Aerating is the act of exposing air into wine. Exposing wine to air does two things: it triggers oxidation and evaporation. Wines that contain some undesirable and volatile components require aeration to evaporate these components, leaving behind the aromatic and favorable aspects of the wine behind. Aerating wine will help the wine age and improve its taste.
WineFrog explains Aerate
Young, full-bodied wines contain tannins that make the wine astringent and removes some extremely delicate flavors. While in older wine, the tannins break down in the bottle as the wine's bouquet evolves, in younger wine, the astringency takes over. By aerating wine, the tannins break down due to the air exposure. This opens up the flavors of the wine, but, it is not wise to aerate old wine for long, as aerating for a prolonged periods may remove a wine’s unique aroma.
You can aerate wine by pouring wine into a decanter and letting it sit, using a spout aerator that attaches to the bottle and aerates wine as it pours into a glass, by pouring wine into a glass and allowing it to sit or simply swirling the glass of wine. For better oxidation, as you pour you can hold the bottle high above the glass without spilling, exposing the wine stream to the air for a longer period of time. After the wine gets oxidized, the aroma and flavors bloom.