Definition
The term airstream mechanisms refers to the manner and place in which airflow is initiated in order to produce speech sounds. Speech can be produced via a pulmonic (lung), glottalic (vocal folds), and velaric (tongue) airstream mechanism, depending on the target sound.
Airstream mechanisms may be either egressive or ingressive. Egressive refers to the outwards flow of air through the vocal tract (i.e., out of the mouth) during speech. Ingressive airflow refers to air coming in the vocal tract during speech.
Examples
INLP Linguistic Glossary 