1. hold* in (d.), keep* back (d.), restrain (d.); (о неприятеле и т. п.) hold* in check (d.), contain (d.); (об агрессии) deter (d.); (о лошадях и т. п.) hold* (back) (d.); (перен.; о чувствах) keep* in (d.); (о слезах, рыданиях и т. п.) suppress (d.), restrain (d.), check (d.)
сдержать смех— suppress a laugh
2.:
сдержать своё слово, обещание— keep* one's word, promise; be as good as one's word идиом.