vi.
沉思,思索,考虑(about, on, upon):
This is the method that we have been speculating about.
这正是我们一直在思考的方法。
推测,猜测 (about,on):
No one can speculate on what he's thinking about.
没人知道他在想什么。
做投机生意；投机：
to speculate on the futures
搞期货投机生意
vt.
推测，猜测：
to speculate one'