vi.

1. 思索；沉思；推测[（+on/upon/about）]
   She speculated about her friend's motives.

   她猜测她朋友的动机。

2. 投机；做投机买卖[（+in）]
   He speculated successfully in mining shares.

   他做矿业股票投机获得成功。

vt.

1. 推测，推断[Y][+that]
   He was speculating that this might be his last chance.

   他推测这可能是他的最后一次机会了。

v.

1. form a theory or conjecture without firm evidence.
2. invest in stocks, property, or other ventures in the hope of gain but with the risk of loss.