If "reconnoiter" means to explore for information:
* Ignore: To completely disregard or pay no attention to.
* Neglect: To fail to care for or attend to.
* Overlook: To fail to notice or consider.
* Dismiss: To reject or disregard something as unimportant.
If "reconnoiter" means to scout or examine:
* Abandon: To leave something behind.
* Withdraw: To retreat or move away from something.
* Neglect: To fail to pay attention to.
* Ignore: To refuse to acknowledge something.
If "reconnoiter" means to survey or inspect:
* Overlook: To fail to notice something.
* Miss: To fail to see or perceive something.
* Disregard: To pay no attention to something.
The best antonym for "reconnoiter" will depend on the specific context and the nuance you want to convey.