Definition of close up in US English:

close up

phrasal verb

  • (of a person's face) become blank and emotionless or hostile.

    ‘he didn't like her laughter and his face closed up angrily’
    • ‘His face closed up and he looked away from her, towards the forest.’
    • ‘She breaks off, her face closing up, her eyes darting away.’
    • ‘Peter turned away from him, his expression closing up.’