EMPHASISE
stress, emphasize, emphasise, punctuate, accent, accentuate
(verb) to stress, single out as important; “Dr. Jones emphasizes exercise in addition to a change in diet”
underscore, underline, emphasize, emphasise
(verb) give extra weight to (a communication); “Her gesture emphasized her words”
Source: WordNet® 3.1
Verb
emphasise (third-person singular simple present emphasises, present participle emphasising, simple past and past participle emphasised)
(British) Alternative spelling of emphasize
Usage notes
The "s" spelling has co-existed with the "z" spelling for at least 150 years (Thackeray wrote emphasised), and is becoming more common in the UK, with the "z" spelling slowly falling out of usage.
Anagrams
• semiheaps
Source: Wiktionary