SHOW A FEELING OR ATTITUDE#not showing your feelings of love or friendliness 含蓄的,感情不外露的
Examples from the Corpus
undemonstrative• Neighbours say he was quiet, undemonstrative and always carefully dressed.• Jennie's performance during his last months and weeks was a model of quiet, undemonstrative heroism.• It is standing firm with the United States, in its clipped and undemonstrative sort of way.