American Heritage Dictionary
(2)
Century Dictionary
GNU Webster's 1913
WordNet
(2)
Elsewhere on the web
Times reporter finds that, for a basket of ten items-including milk, seltzer, and frozen pizza-a shopper would save $6.01, or 13 percent.— Inc.com
This simple, refreshing mix of lemon juice, sugar, gin, and seltzer has been around for at least a century and a half.— Esquire.com Article Feed
On Sunday he had eight glasses of hollands and seltzer--a shilling each, a pint of stout and some cider, besides half a dozen cigars or so.— Immortal Memories

American Heritage Dictionary (1)
Bubble size: how much this word was used in a year
Bubble height: used more or less than expected, vs. all uses evenly distributed
You can expect to see this word a few times a year.