1 [mass noun] the action or process of investing money for profit:a debate over private investment in road-buildingthe need to attract foreign investment [count noun]:a total investment of £50,000
[count noun] a thing that is worth buying because it may be profitable or useful in the future:freezers really are a good investment for the elderly
[count noun] an act of devoting time, effort, or energy to a particular undertaking with the expectation of a worthwhile result:the time spent in attending the seminar is an investment in our professional futures
2 [mass noun] archaic the surrounding of a place by a hostile force in order to besiege or blockade it.
investment in other Oxford dictionaries
Definition of investment in the US English dictionary