by pointing with your whole hand vertical, palm facing inward, fingers together, you are indicating a firm diasgreement with something.
During a game of beer pong where the ball bounced twice on the rim of one cup then fell to the floor, Nick gave the cup the firm disagree by pointing his hand at it.
When one enters ones extremely hot bath, his/hers scrotum sack becomes very firm and begins to look like a small dry brain
"oh ouch this bath seems to be slightly to hot, it is beginning to give me a firm sack, better add some cold water before it looks anymore like a brain"