Silly String
/ˈsɪli strɪŋ/originally US
noun
A synthetic resin-based substance, usually brightly coloured, which is sprayed from an aerosol can as a foam, and solidifies as a light, flexible, slightly sticky string, typically used as a children's toy, or as an alternative to party streamers.
- A trademark in the United States..
Origin
1970s; earliest use found in The Washington Post. From silly + string.