1. Not able to be counted (e.g. because too many to count) 
2. (grammar) of a word that does not have a plural form

Encyclopedia: Uncountable

• Sesbania grandiflora
• Seseli
• Sesotho
• sesqui-
• sesquicentenary
• sesquicentennial
• sesquipedalia
• sesquipedalian
• sesquipedality
• sess
• sessile
• sessile polyp
• sessile trillium
• session
• session cookie
• sessional
• Sessions
• sesterce
• sestertius
• sestet
• sestina
• set
• set ablaze
• set about
• set afire