To explore; to view, inspect, and examine secretly, as a country; -- usually with out.

A person sent secretly into an enemy's camp, territory, or fortifications, to inspect his works, ascertain his strength, movements, or designs, and to communicate such intelligence to the proper officer.

secretly collect sensitive or classified information; intentionally do something in a hidden way that people will not know about, "spy for the Russians using a spy camera".

(military) a secret agent hired by a state to obtain information about its enemies or by a business to obtain industrial secrets from competitors

AMEX tracking stock that represents the S&P 500

First and largest ETF, Standard & Poor's Depositary Receipts (SPDRs) track the S&P 500 and are pronounced just like the name for arachnid.

Amex-traded ETF tracking the "large-cap" S&P 500 Index.

The S&P 500 index tracking stock and first of the SPDRs. This is one of the largest and most popular Exchange Traded Funds (ETF).

To gain sight of; to discover at a distance, or in a state of concealment; to espy; to see.

To discover by close search or examination.

catch sight of