sungmoo认为：

个人理解，市场出清指市场中供求相等，而瓦尔拉均衡指市场中（每种商品都）没有正的超额需求。市场上所有商品都出清是瓦尔拉均衡的一种情形。如果存在免费商品，则瓦尔拉均衡未必是所有商品都出清。如果“均衡”还有别的含义，须先指出其含义再谈与“出清”的关系。

xianghua005认为：

当然不是。均衡是指在没有外生扰动时，系统保持稳定。均衡不见得市场出清，比如钱颖一的搏弈论模型均衡与市场短缺相联系，在许多动态模型中随时间的流逝均衡结构会发生自发演进。

jerryren认为：

“market clearing.if demand equals supply in k-1 markets,and pk>0,then demand must equal supply in the kth market”

详细出处参考：http://bbs.cenet.org.cn/dispbbs.asp?boardID=92507&ID=80343

In economics, market clearing refers to either

1. a simplifying assumption made by the new classical school that markets always go to where the quantity supplied equals the quantity demanded; or
2. the process of getting there via price adjustment.

The core idea is that the market will eventually be cleared of all surpluses and shortages (excess supply and demand). The first version assumes that this process occurs instantaneously.

简译下

在经济学中，市场清出是指

1）新古典主义学派的一个简化假设：市场总是趋向达到供给量等于需求量的状态；或，

2）达到上述状态的价格调整过程。

其核心思想是，市场上所有（超出供给和需求的）过剩和不足 最终都将被清除。最初的理论则假设该过程是在瞬时发生的。

后面还有一段说，

In the short run (and possibly in the long run), markets may find a temporary equilibrium at a price and quantity that does not correspond with the long term market clearing equilibrium. For example, in the theory of "efficiency wages," a labor market can be in equilibrium above the market-clearing wage, since each employer has the incentive to pay wages above market-clearing to motivate their employees on the job. In this case, equilibrium wages (where there is no endogenous tendency for wages to change) would not be the same as market-clearing wages (where there is no classical unemployment).

从短期来看（或许也可以从长期看），市场可能在某个价格和数量水平上搜寻到暂时的均衡点，但该价格和数量水平和长期上市场清出时的均衡并不相同。

比如，在“效率工资”理论中，由于每个雇主都企图支付高于劳动力市场清出时的工资来激励雇员工作，劳动力市场就可以在市场清出条件下取得的工资水平之上达到均衡。该例中，均衡工资（此时不存在工资变化的内生趋势）将不等于市场清出条件下的工资（此时不存在失业）。

http://en.wikipedia.org/wiki/Market_clearing