The way the words "dash of" or "pinch of" refer to adding some ingredient in small amounts, is there a similar (cooking) term for adding large quantities of something?
I'm not sure what part of speech you want (a sample sentence would help—see the SWR tag's guidance), but the adjective "generous" and adverb "generously" are often used for this purpose. For example:
When the mixture has browned, add a generous amount of tomato sauce (recipe 6) or tomato paste diluted with water. . . . Be sure to serve the fish nicely covered with a generous amount of the thick sauce it has been cooking in. (Pellegrino Artusi, "Science in the Kitchen and the Art of Eating Well," University of Toronto Press, 2003, pg. 330)
Sprinkle generously with sugar and return the cobbler to the oven and bake until golden, about 15 minutes. (Alaska Northwest Books, "The Alaska Homegrown Cookbook," West Margin Press, 2011)
By the way, "dash" and "pinch" may be used to designate precise amounts. However, you can easily find terms for precise large amounts, so I assume that that's not what you wanted.
Slather is a term meaning to spread thickly. It's not strictly a food word, but may be used to describe how butter, jam, or other condiments are applied to a food.
Another term often found in recipes is to an add ingredient like salt or seasoning liberally, which means you should add an unspecified large quantity.
Heaping is another term used in recipes to describe a quantity that is an unspecified amount more than a certain measured quantity - it may not be a large amount in an absolute sense, but it's bigger than the measured amount. A heaping tablespoon, for example, is a quantity somewhat larger than a tablespoon by a non-specific amount.