Entry 1 sense Webster, 1913 Seaside /sēs'-īdˌ/ · Sea·side · IPA /ˌsiːˈsaɪd/ 01 n. The land bordering on, or adjacent to, the sea; the seashore. Also used adjectively. 1. The land bordering on, or adjacent to, the sea; the seashore. Also used adjectively.