Arabic word used to express frustration or anger. The "7" is a gutteral "h" sound. It sounds like an exgagerated Sherlock Holmes "aha!". Its literal meaning is the sound of a woman's orgasm. This sexual background is responsible for making "a7a" considered to be vulgar. But "a7a" is loyally used by many Egyptian teenagers and young adults. While "a7a" is used mostly in Egypt, it is attracting a small following in other Arab countries as well.
One can reply to an "a7a" by saying "a7atein" (literally: two "a7a"'s).
"a7a I missed my bus"
"a7a that khawal
stole my wallet"
"a7a I can't believe this shit"