A slang term given to investors or other market participants who ignore important pieces of information or situations, which have the ability to impact them or the market in which they operate. The reasons behind type of action can include risk aversion and bias.

The investment term is derived from the similarities between investors and these large birds, where in response to a dangerous situation, they stick their heads in the ground. These participants will ignore the market at all costs when it is not working to their advantage, in effect sticking their 'heads in the ground' in response to the stress of the market.