1. extremely; very (used for emphasis, often expressing annoyance)
Usage: informal
2. in a way relating to or resembling hell
Usage: literary

Examples

• The traffic was moving infernally slowly.
• It’s infernally hot in this room.
• The machine makes an infernally loud noise.
• He was infernally difficult to work with.
• The flames danced infernally in the darkness.
• She found the puzzle infernally challenging.