Astaghfirullah literally translates to "I seek forgiveness in Allah". In a religious way, people can recite it during meditation or say it to others to show humility- to say that Allah is greater or that goodness comes from Allah. In popular culture, people can say this if they see something wrong or shameful (context applies).
Example 1:
Person- Hatija, your lecture was truly insightful!
Hatija- Astaghfirullah, Allah gives us the knowledge.
The most amazing guy you'll ever meet. Loving, caring, handsome with questionable sexual preferences - Ashtavious is an avid animal lover, spending countless hours with his dogs. He's also a master in the kitchen when creating his own recipes with weird ingredients like peanut butter. Ashtavious is as strong as an ox and can always be counted on. Becoming friends with Ashtavious is as easy as pie. He can be found in many places such as the bar, the bathroom, any local dog park, or any other communal areas.
An ugly ass, a nasty ass. A reference to the "city" of Ashtabula in Ohio and its ugly ass inhabitants. Can also be used to describe an ugly blemish or physical flaw.