abysmal (adj.)

• abyssal
• appalling
• astronomic
• awful
• bottomless
• cavernous
• colossal
• dreadful
• elephantine
• enormous
• epic
• gaping
• giant
• gigantic
• heroic
• huge
• illimitable
• immense
• infinite
• jumbo
• mammoth
• mighty
• monstrous
• monumental
• mountainous
• prodigious
• profound
• soundless
• stupendous
• terrible
• titanic
• towering
• tremendous
• unfathomable
• unfathomed
• unsounded
• vast
• yawning