A word to describe the point of land at the confluence of two rivers?

Perhaps its could be termed a peninsula?

A piece of land almost surrounded by water or projecting out into a body of water. — Oxford Dictionaries

Wikipedia mentions peninsula used for the land where a river which courses through a very tight meander which seems similar to OP's requirement. Assuming here the term can be used regardless for the surrounding waters' direction of flow.

A peninsula (Latin: paeninsula from paene "almost" and insula "island") is a piece of land extending out into a body of water that is still connected to mainland, or a piece of land that is bordered by water on three sides but connected to mainland. [...] The surrounding water is usually understood to be continuous, though not necessarily named as a single body of water. Peninsulas are not always named as such; one can also be a headland, cape, island promontory, bill, point, or spit. [...] A river which courses through a very tight meander is also sometimes said to form a "peninsula" within the (almost closed) loop of water.

Although not exactly a single word, however, according to Wikipedia, the phrase river delta can be used to describe the land formation which forms at the point where two rivers meet.

From Wikipedia:

A river delta is a landform that forms from deposition of sediment carried by a river as the flow leaves its mouth and enters slower-moving or standing water. This occurs where a river enters an ocean, sea, estuary, lake, reservoir, or (more rarely) another river that cannot transport away the supplied sediment.

MESOPOTAMIA means 'land between two rivers'; DOAB in Hindi means 'tongue'; TONGUE (according to OED) means: III. Anything that resembles or suggests the human or animal tongue by its shape ... 13. A tongue-like projecting piece of anything ... a. A narrow strip of land, running into the sea, or between two branches of a river, or two other lands ... (attestations between 1566 and 1857, so Middle-English usage). So, "tongue" is your best bet.

The land mass formed by a confluence can also be called a point. A beautiful example is in Pittsburgh, PA. This land mass is formed by the joining of the Allegheny and Monongahela Rivers to create the Ohio River, hence it's name, "The Pointe", which is the French word for point. The Pointe, Pointe State Park, and the original foundation of Fort Pitt are located on the epicenter of this point.